Muslims often argue that the Bible is reliable where the Qur’an confirms it, but corrupted where it contradicts the Qur’an. Fair enough. How does the Quran confirm the Bible? Believe it or not, in some very trinitarian ways. In Surrah 3:45 the Quran says "When the angels said, ‘O Mary, indeed Allah gives you good news of a Word from Him. His name is the Messiah, Jesus son of Mary, distinguished in this world and the Hereafter, and among those brought near.’ What's interesting is that the Quran itself doesn't provide any explanation of the way in which Jesus is the Word. It's also interesting that this Word is personal and has a name. Since the Quran is confirming the Bible in this passage, I think the natural place to go to understand what it means for Jesus to be the Word, is John 1. That's where we see the Word as both God and with God. So it at least seems like the Quran is confirming that aspect of Jesus' nature. Surrah 4:171 is also very interesting in the way it confirms the Bible. It says "O People of the Book, do not exceed the limits in your religion, and do not say about Allah except the truth. The Messiah, Jesus son of Mary, was only the messenger of Allah, and His Word which He cast to Mary, and a Spirit from Him. So believe in Allah and His messengers, and do not say, “Three.” Stop; it is better for you. Allah is only one God." How interesting is this? We get Jesus identified as Allah's Word again, but now we also see the "Spirit from him". Obviously, Him in this verse is Allah. But here's the even more interesting part, the author of the Quran seems to understand the relationship between Allah, His Word (Jesus), and the Spirit. Immediately before this statement, Allah reminds them that there's a boundary to the religion that shouldn't be crossed. And then after it says "Do not say Three." Stop. It is better for you. Allah is only one God." So we see here that even though you have Allah and Jesus, His Word, and His Spirit, we still only have one God. And the boundary that shouldn't be crossed is saying that there are three. That's extremely trinitarian.