I saw this coming, which is why I commented recently on whether Christians and Muslims worship the same God. The Qur’an, in a fashion, says yes:
And say, “We believe in that which was sent down unto us and was sent down unto you; our God and your God are one, and unto Him are we submitters.” Q 29:46
But what does this assume? That the author of the Qur’an understood what “our God” (that is, the God of the People of the Book) would mean. And it is just here that we must point out that there is nothing in the text of the Qur’an to give believing Christians any reason to believe the author of the Qur’an actually understood Christian teaching on the nature of God. The repeated warning of the Qur’an against saying “three” while directly connecting this ordinal number with the counter-balanced “there is only one God,” together with the conjunction of Allah, Mary, and Jesus in Q 5:116, along with the troubling phrase, “truly God is the third of three” (Q 5:73), all reveal a dismal ignorance of what sonship, the deity of Christ, the incarnation, etc., actually meant in Christian theology. And let’s remember the Qur’an speaks of unbelief, idolatry, and the “final refuge shall be the Fire,” for those who say “three.” Muslims have come up with a number of ways of understanding these texts, but it seems plain that it is the intention of the Qur’an to strongly condemn as “excess” the central affirmation of the Christian faith: that God has revealed Himself as Father, Son, and Holy Spirit, and this has been done in its clearest expression in the Incarnation of the Son, and the outpouring of the Holy Spirit. Indeed, one of the central dogmatic texts of the Qur’an, Surah al-Ikhlas, has as its third ayah, “He begets not; nor was He begotten.” While it is heartening to read the commentary provided in the new Study Qur’an which seeks to disconnect this text from having relevance to Christianity, the vast majority of Muslims have read it as having such relevance, and numerous early tafsir sources, as I recall, do likewise.
In any case, the Christian God is not a transcendent unitarian monad. The Christian God has always been intimately involved in His creation, and has always been fulfilling His purpose which has always, from the time of creation, been focused upon Calvary—all of history looked forward to the Cross, all of history looks back upon it. I realize this is an amazing claim to make, even for Christians today, but a brief consideration of such texts as Ephesians 1 or Romans 8 would bear this out. And when one realizes that Christians are actually saying that the eternal Son of God entered into human flesh and lived as Jesus of Nazareth, then how else could it be? So the Triune God has been personally involved in the accomplishment of His own glorification from the beginning of time. It has always been His intention to unite a people to Himself through the Son, in grace and love, and to provide for them eternal life and union with Him. As John saw in the heavenly realms in the Spirit, all of creation bows and worships Him who sits upon the throne (the Father), and the Lamb (the God-man who gave Himself as the sacrifice). The pure worship to which creation moves involves the personal revelation of Father, Son, and Spirit.
So if the great God of eternity has revealed the truth of the Trinity through the Incarnation of the Son and the outpouring of the Holy Spirit, is it truly possible that one can reject that revelation (and the self-giving of the Son on Calvary) and still have as the object of his or her worship that one true God whose witness he or she has rejected? If the Son truly was the Second Person of the Trinity incarnate, and if all of creation will someday bow the knee and declare Him Lord, how can one who rejects this revelation be said to be worshipping God? True, deep, confessional Christian worship is triune in nature.
So while on a surface level one can say “Christians and Muslims claim to worship the one God of Abraham,” it is, in my opinion, disrespectful to BOTH positions to refuse to go farther than that. The believing Christian believes that same God then did something amazing and universe-changing in the coming of the Son and the Spirit. The Muslim rejects these central claims and makes its central religious assertion tawhid, the unitarian oneness of Allah. Just as Christian worship is inalterably trinitarian, Islamic worship is inalterably unitarian. So how can it be anything other than disrespectful to both to conflate them to a least common denominator level so that we can “get along”? How much depth is there to such a conclusion? And how far can it get us in the necessary discussion of our deep differences?