For witnessing to Muslims we must be aware of their key presuppositions, not just the fact that Muslims deny the Trinity and Deity of Christ for example, but why they deny them, so that we can confront their presuppositions directly and avoid getting side tracked when witnessing to Muslims. Before proceeding further it is necessary to briefly address the view of the Quran and Hadeeth in orthodox Islam, what are they and what role do they play in Islamic theology. According to orthodox Islam the Quran eternally existed in the Arabic language and was later revealed to Muhammad who recited it and his followers passed it on via oral tradition and it was later written down and recorded after Muhammed died. Their view of scripture is dictation, Muhammad was in no way the author of the Quran in orthodox Islam (a view taken by liberal Muslim scholars), Muhammad was merely a medium to present the revelation. The Quran is divided into chapters (surah) and verses (ayah), the Quran is not written in chronological order, but more topically based, there is an Arabic name for each chapter of the Quran giving its main theme. There is a twofold distinction of surahs written in either Medina or Mecca. Meccan surahs reflect Islam prior to Muhammad political rule and Medinnan surahs reflect Islam once Islam has gained political power, which accounts for some of the differences between some sections of the Quran. In addition to the Quran are the Hadeeth, recordings of the saying and teachings of Muhammad, they expand upon the majority of the verses in the Quran and there by provide an early commentary and authoritative explanation of key passages. The 2 primary and most reliable Hadeeth are called Saheeh al Bukhari and Saheeh Al Muslim.
Here is a summary of the major presuppositions that Muslims believe which are important for witnessing to Muslims. I’ll be focusing on Tawheed since this is crucial to how every Muslim views the Bible and how they view their salvation.
- Tawhid/Tawheed– Allah is one in being and person (precludes polytheism and the doctrine of the Trinity), this includes the teaching that Allah has no son. This is represented in the well known basic Islamic statement of faith, the shahadah, “there is no God but Allah, and Muhammad is his messenger”.
- Breaking Tawhid is known as shirk, associating partners with Allah.
III. The Quran addresses Jews and Christians (called Ahl-al-Kitab in Arabic, Ahl-al-Injil, used to refer to Christians specifically), but the OT & NT are considered corrupted, while the Arabic text of the Quran has eternally existed in the Arabic language and was revealed to Muhammad and written down after his death, and preserved with no changes.
- The Quran Denies the crucifixion of Jesus [Jesus is referred to as Isa in the Quran], Surah 4:157-158
- Islam claims to be in continuity with the teachings of the previous Abrahamic religions (Judaism and Christianity), and Muhammad is the final prophet in the chain of prophets from Adam to Isa [Jesus] culminating in Muhammad
- In recent Dawah, the Apostle Paul is attacked as the originator of the corruption of Christianity, creating the doctrines of the Trinity and Deity of Christ.
VII. There is no assurance on judgment day for Muslims, assurance of salvation is dependent on whether Allah is merciful and will let them go to heaven, scales of good and bad works weighed to determine whether someone goes to heaven or hell.
As Christians we affirm monotheism, but it is important to understand that according to tawhid Unitarian monotheism is presupposed (Allah is one being and one person), so even a plurality of persons that is one substance (the doctrine of the Trinity) is still considered a violation of Tawhid. The Trinity is perceived by Muslims as not being much different from the polytheism of Hinduism. Here is a basic definition of the nature of God’s oneness (Tawhid) in Islamic theology,
“The Unity of God according to the Qur’an, implies that God is One in His person (dhāt), One in His attributes (ṣifāt) and One in his works (af’āl). His Oneness in His person means that there is neither plurality of gods nor plurality of persons in the Godhead; His Oneness in attributes implies that no other being possesses one or more of the Divine attributes in perfection…”.
Examining the Quran’s teaching of the doctrine of tawhid, the most important Surah is Surah Al-‘Ikhlas (112:1-4), “Say, “He is Allah, [who is] One, Allah, the Eternal Refuge. He neither begets nor is born, Nor is there to Him any equivalent”. This verse uses the same semitic root for the verb “to beget” as occurs in Isaiah 9:6, making this verse an explicit denial of the incarnation of Christ.
In contrast to tawhid, is shirk, which is a violation of tawhid by associating partners with Allah, whether that is the Trinity or polytheism, and even extends to mystic forms of idolatry. Muhammad Ibn ‘Abdul-Wahhab defined the grave nature of shirk as follows,
“The opposite of complete tawheed is defined in Islam as shirk, Shirk literally means to take partners with Allah in any aspect of His divinity. Shirk is the antithesis of Islam, which is based on the belief that full acceptance of tawheed leads to eternal salvation and corruption of tawheed leads to damnation”.
So based on Islamic theology, when Christians present the Gospel to a Muslim they perceive the Gospel as an invitation to commit [major] shirk and be eternally damned.
The first of the three categories of tawhid is Unity in Allah’s Lordship (Tawhid ar-Rububiya), Rububiyah comes from the Arabic word Rabb for Lord, it is a declaration of the unique sovereignty of Allah. Quranic support for oneness in Allah’s lordship is well attested,
“Allah created all things and He is the agent on which all things depend” (Surah 39:62).
“And Allah created you all and whatever you do” (Surah 37:96).
“And no calamity strikes except by Allah’s permission” (Surah 64:11).
Rububiyah also precludes charms and wearing Quranic verses because of its pagan practices, only Allah is to be viewed as sovereign and a Muslim is to trust in nothing or no one else but Allah.
The second category of Tawhid is that Allah is one in his name & attributes (Tawhid al-Asma’ waṣ-ṣifat), which can be divided into 5 categories. The first is the unity of Allah’s names and attributes; Allah’s attributes are only those attributes to Allah in the Quran, and all of God’s attributes are absolute, free from any human deficiencies, and therefore qualitatively distinct from human attributes rather than only being distinguished quantitatively. The second aspect is similar, Allah cannot be given any new name, he can only be called by what he calls himself or Muhammad calls him in the Quran. The third aspect is that Allah cannot be given any attributes of his creation, and some descriptions of Allah hearing or seeing are to be understood as Allah’s abilities being perfect, not synonymous with man’s abilities. The fourth aspect precludes giving any of the names or attributes of Allah to man, Dr. Abu Bilal cites Hebrews 5:5-6 and 7:1-3, attributing eternality to Jesus as an example of breaching this aspect of Tawhid. The fifth and last aspect of Tawhid al-Asma’ waṣ-ṣifat teaches that the names of Allah can only be given to another if it is prefixed by ‘abd, “slave of/servant of,” because in their indefinite form they represent perfection which belongs to Allah alone, not even Muhammad can be called by a divine name with this prefix and calling oneself an ‘abd of Muhammad or anyone else is a violation of Tawhid.
The third category of Tawhid is Oneness in Allah’s right to be worshipped (Tawhid al-‘Ibadah), which must be accompanied with the former two categories to be considered complete Tawhid in Islam. Dr. Bilal Phillips explains why this third category is the most crucial category of Tawhid,
“All forms of worship must be directed only to Allah because He alone deserves worship, and it is He alone who can grant benefit to man as a result of His worship. Furthermore, there is no need for any form of intercessor or intermediary between man and God”.
This is emphasized in the first Surah of the Quran (Surah al-Fāṭiḥah), which must be recited by Muslims 17 times each day, “It is to You [Allah] we worship and You we ask for help” (Surah 1:5). Islam teaches that this is the view of both previous Abrahamic religions (Judaism & Christianity), that all of the prophets (including Jesus) taught Tawhid,
“Abraham was neither a Jew nor a Christian, but he was one inclining toward truth, a Muslim [submitting to Allah]. And he was not of the polytheists” (Surah 3:67).
“And I did not create the jinn and mankind except to worship Me” (Surah 51:56).
Also this third category of Tawhid combines the political aspect of Islam (Sharia) with its theology because ‘Ibadah means total obedience, and because Allah is the ultimate lawgiver this requires implementing Sharia law, all secular forms of law demonstrate disbelief in Allah’s divine law and is shirk. Dr. Abu Bilal advocates this even more forcefully that Muslims cannot be neutral concerning the implementation of Sharia in government,
“Hence, a significant part of Tawhid al-‘Ibadah involves the implementation of Shariah, especially in lands where Muslims form the majority of the population…The acceptance of non-Islamic rule in place of Shariah in Muslim lands is shirk and an act of kufr [disbelief in Allah]. Those in a position to change it must do so, while those unable to do so must speak out against the rule of kufr and call for the implementation of Shariah”
Another crucial aspect of tawhid is how the Quran expresses the doctrine of the Trinity since the Trinity is considered shirk, breaking tawhid, it ought to have a proper understanding of the Christian doctrine of the Trinity given that the Council of Nicaea had already occurred in the 4th century, so the Christian position on the doctrine of the Trinity was unambiguous at the time of Muhammad, 600 AD. However the Quran reveals otherwise, demonstrating the author of the Quran did not understand the doctrine of the Trinity,
“And [beware the Day] when Allah will say, “O Jesus, Son of Mary, did you say to the people, ‘Take me and my mother as deities besides Allah?'” He will say, “Exalted are You! It was not for me to say that to which I have no right. If I had said it, You would have known it. You know what is within myself, and I do not know what is within Yourself. Indeed, it is You who is Knower of the unseen. I said not to them except what You commanded me – to worship Allah , my Lord and your Lord. And I was a witness over them as long as I was among them; but when You took me up, You were the Observer over them, and You are, over all things, Witness” (Surah 5:116-117).
Notice that not only does the Quran teach that all of the prophets accepted Tawhid, Surah 5 also gives an explanation of how the Quran understands the Christian doctrine of the Trinity, according to Surah 5:116-117 the trinity consists of Allah, Jesus, and Mary, which is found nowhere in the Bible. Another important Surah in the Quran that attempts to describe the Christian doctrine of the Trinity is Surah 4:171-172,
“O People of the Scripture, do not commit excess in your religion or say about Allah except the truth. The Messiah, Jesus, the son of Mary, was but a messenger of Allah and His word which He directed to Mary and a soul [created at a command] from Him. So believe in Allah and His messengers. And do not say, “Three”; desist – it is better for you. Indeed, Allah is but one God. Exalted is He above having a son. To Him belongs whatever is in the heavens and whatever is on the earth. And sufficient is Allah as Disposer of affairs. Never would the Messiah disdain to be a servant of Allah, nor would the angels near [to Him]. And whoever disdains His worship and is arrogant – He will gather them to Himself all together” (Surah 4:171-172)
This is not something novel in Islamic theology, but is testified by early primary Islamic scholars such as the renown Islamic commentator Ibn Kathir,
“Believe that Allah is One and Alone and that He does not have a son or wife. Know and be certain that ‘Isa [Jesus] is the servant and Messanger of Allah. Then immediately thereafter (“Say not: ‘Three!”), do not elevate ‘Isa and his mother to be gods with Allah. Allah is far holier than what they attribute to him”.
Likewise 12th century Islamic scholar Abu al-Qasim Mahmud ibn Umar az-Zamakh-shari views this passage and the Quran as a whole teaching that Christians view the Trinity as polytheism consisting of the three gods: The Father, Mary, and Jesus,
“According to the evidence of the Quran, the Christians maintain that God , Christ, and Mary are three gods, and that Christ is the child of God by Mary, as God says (in the Quran): ‘O Jesus son of Mary, didst thou say unto men: “Take me and my mother as gods, apart from God”?’ (5:116), or : ‘The Christians say: “The Messiah is the Son of God” (9:30). Morever, it is well known that the Christians maintain that in Jesus are (combined) a divine nature derived from the Father and a human nature derived from his mother…At the same time these words [4:171] exclude (the Christian view) that Jesus had with God the usual relationship between sons and (their) fathers…”.
A major problem with the Muslim argument that the Bible is corrupted is that the Quran commands the Ahl-al-Kitab to judges by their scriptures, but how can they judge by their scriptures if they are already corrupted? There are two different types of corruption: tahrif al-mana (corruption of meaning) and tahrif al-nas/al-lafz (corruption of the text). In light of the context of Surah 5:42-48, 65-68 and other Quranic texts which explicitly deny that the words of Allah can be corrupted (Surah 6:114-115, 18:27), and other Surah stating that the People of the Book have concealed the truth (Surah 3:69-72), tahrif al-mana provides the most consistent explanation without making the Quran contradict itself since Surah 5:42-48, 65-68, would be a useless command to the people of the book (Jews and Christians) if the Torah and Injil were already corrupted (tahrif al-nas/al-lafz) by the time of Muhammad. In the context of Surah 5:43-47, the Jews come to Muhammad who is ruling in Medina and ask him about how to judge over a dispute they are having and Muhammad tells them to judge by what God has given them in the Torah, and he addresses the Christians and tells them to judge by what God has revealed to them as well,
Surah 5:43-47 (Surat Al-Mā’idah) “But how is it that they come to you for judgement while they have the Torah, in which is the judgement of Allah ? Then they turn away, [even] after that; but those are not [in fact] believers.  Indeed, We sent down the Torah, in which was guidance and light. The prophets who submitted [to Allah ] judged by it for the Jews, as did the rabbis and scholars by that with which they were entrusted of the Scripture of Allah , and they were witnesses thereto. So do not fear the people but fear Me, and do not exchange My verses for a small price. And whoever does not judge by what Allah has revealed – then it is those who are the disbelievers. And We ordained for them therein a life for a life, an eye for an eye, a nose for a nose, an ear for an ear, a tooth for a tooth, and for wounds is legal retribution. But whoever gives [up his right as] charity, it is an expiation for him. And whoever does not judge by what Allah has revealed – then it is those who are the wrongdoers.  And We sent, following in their footsteps, Jesus, the son of Mary, confirming that which came before him in the Torah; and We gave him the Gospel, in which was guidance and light and confirming that which preceded it of the Torah as guidance and instruction for the righteous.  And let the People of the Gospel judge by what Allah has revealed therein. And whoever does not judge by what Allah has revealed – then it is those who are the defiantly disobedient.”
The argument continues a few verses (ayat) later, Muhammad commands the Christians to test the Quran by what has come before it, the Old and New Testament,
Surah 5:65-68 (Surat Al-Mā’idah) , “And if only the People of the Scripture had believed and feared Allah , We would have removed from them their misdeeds and admitted them to Gardens of Pleasure.  And if only they upheld [the law of] the Torah, the Gospel, and what has been revealed to them from their Lord, they would have consumed [provision] from above them and from beneath their feet. Among them are a moderate community, but many of them – evil is that which they do.  O Messenger, announce that which has been revealed to you from your Lord, and if you do not, then you have not conveyed His message. And Allah will protect you from the people. Indeed, Allah does not guide the disbelieving people.  Say, “O People of the Scripture, you are [standing] on nothing until you uphold [the law of] the Torah, the Gospel, and what has been revealed to you from your Lord.” And that which has been revealed to you from your Lord will surely increase many of them in transgression and disbelief. So do not grieve over the disbelieving people.”
This provides the route by which we directly challenge a Muslims’ affirmation of the authority of the Quran as well as the incorrect view that the Trinity consists of Allah, Mary, and Jesus. Muslims are using a double standard when they cite Bart Erhman or other skeptics to attack the reliability of the Bible, when the Quran commands Christians to judge by what God has revealed in the Bible. We can go back to the prophets and demonstrate that the God of the Bible is holy as observed in Isaiah’s vision in Isaiah 6 in contrast to the view of god in the Quran, and God is revealed as perfectly Just (Proverbs 17:15). A Muslim has no assurance on judgment day that Allah will be merciful and let him or her get into heaven by their own deeds, but as Christians we have a blessed hope, not by our own righteousness by Christ’s perfect righteousness (Romans 3:23-25, 5:1).
 Muhammad Ali breaks down the Arabic of the first part of the Shahadah, the Kalimah at-Tawheed, statement of Allah’s Unity, “The best known expression of Divine Unity is that contained in the declaration of la ilaha ill-Allah. It is made up of four words, la (no), ilah (that which is worshipped), illa (except) and Allah (the proper name of the Divine Being)” Maulana Muhammas Ali, The Religion of Islam (Ahmadiyya Anjuman Ishaat: Columbus, Ohio, 1989), 109.
 This was a shift in Islamic Dawah in the 20th century, which did not exist as the majority view of Muslims in preceding centuries who viewed the OT & NT as corrupted in its meaning (tahrif al mana) rather than the actual texts being corrupted (tahrif al-nas), “In the mid-19th century, the Muslim accusation of tahrif al-nass took a kind of quantum leap through the controversy between Indian Muslim scholars and European Christian missionaries in the India of the British Raj…Mawlana Rahmat Alllah Kayranawi (“al-Hini,” 1818-91) is credited with moving the textual corruption accusation forward through a famous public debate and through a widely published book. Interestingly, the most influential Indian theologian of the modern period, Shah Wali Allah (1703-62), had previously declared that he did not believe in the corruption of the text of the Torah…Rahmat Allah seized upon a strategic plan for publicly confounding European Christian missionaries…For the first time in the history of Muslim polemic, the Indian theologian used works of historical criticism written in Europe to support the claim that Christians themselves knew of the corruption of the Bible. The substance of Rahmat Allah’s polemic in the debate…appeared in print…in the Arabic Izhar ul-haq…20th century Arabic authors did not add substantially to Rahmat Allah’s polemic”. Narratives of Tampering in the Earliest Commentaries on the Quran (Leiden: Brill, 2011): 24-25; cited in James White’s book, What Every Christian Needs to Know about the Quran (Grand Rapids, MI: Bethany House Publishers, 2013), 190
 Ibid, 109; Islam claims to be the only Abrahamic religion that has preserved Tawhid, “Yet, according to the Islamic Unitarian concept (Tawhid), Christianity is classified as polytheism and Judaism is considered a subtle form of idolatry”. Dr. Abu Ameenah Bilal Philips, The Fundamentals of Tawhid (Islamic Monotheism), (International Islamic Publishing house: Saudi Arabia, 2005), 11
 Muhammad ibn ‘Abdul-Wahhab (author), Sameh Strauch (compiler & translator), Kitab At-Tawheed Explained (International Islamic Publishing House, Saudi Arabia, 2010), 22.
 Muhammad’s common statement affirms this, “La ḥawla wa la quwwata illa billah.” (There is no movement nor power except by Allah’s will), ibid, 22.
 Translation from Abu Philips, ibid, 22
 Translation from Abu Philips, ibid, 22
 Translation from Abu Philips, ibid, 22
 Ibid, 26-27
 Ibid, 29-30
 Ibid, 30-31
 Ibid, 34
 Dr. Abu Ameenah Bilal Philips, The Fundamentals of Tawhid (Islamic Monotheism), (International Islamic Publishing house: Saudi Arabia, 2005), 39-40
 Ibid, 41
 Tafsir Ibn Kathir (Riyadh: Darusalam, 2003), 3:59
 Helmut Gatje, The Quran and its Exegesis (Oxford: Oneworld, 2004), 126-127; cited by James White, What Every Christian Needs to Know about the Quran (Bethany House Publishers: Grand Rapids, MI, 2013), 85
 For further discussion on this topic see chapter 8, Did the “People of the Book” Corrupt the Gospel? In James White’s book, What Every Christian Needs to Know about the Quran, 165-192
 This is a good video from the closing statement of a debate with a Muslim apologist in which James White clearly states the Gospel and contrasts the view of justification on judgment day in the Quran with the Bible: