What to know The subject of prophecy in the Bible - specifically, the fact that Jesus fulfilled prophecy - can bring to mind the Islamic claims that Mohammad also bears the honor. Pause first to consider this phrase itself: "Bears the honor." To have been longed for, to have been spoken about before your birth, to have been the subject of mankind's yearning...this is an incredible truth about Jesus al-Masih that we often minimize, as if it were small. But to your Muslim friend, and particularly, to those in a Shame/ Honor worldview, it may be enormous.
So what is your friend talking about? Mohammad, in the Bible?
To begin, your friend isn't referring to Matthew 7:15-20! In the Qur'an, Suras 7:157 and 61:6 are understood by Muslims to mean that Mohammad is the subject of prophecy in the Bible...and many Muslims have been told that he was written about in Deuteronomy 18:18, Song of Solomon 5:16, and John 14-16 (in Jesus's description of the Holy Spirit, Rouh al-Qudus).
Refutations from Christians scholars are available to discuss each one of these claims, showing that Mohammad is not the subject of the verses in Deuteronomy, Song of Solomon, or John. However, because this overview is intended as a Bible-study guide rather than a resource for polemics, we'll suggest another approach. What to say Read the passages that your friends believe about about Mohammad together with your friend. Read them in full, within their context: all of Deuteronomy 17, Song of Solomon 5, and John 14-16. When reading that passage in John, if your friend is willing, back up even further to also read John 12 and 13, to see what comes directly before these words from Jesus.
Do this with a posture of humility, gentleness, and grace. Remember that "Knowledge puffs up, but love builds up" (1 Corinthians 8:1). Let the questions and claims that your friend raises become open doors to meet them where they're at. Together, explore what the Word of God says in these passages. Let your friend express why it was meaningful for them to seek out Mohammad in the Bible...and how they process the Qur'an's claims in light of what the passages say. Don't be surprised if they fall back to saying that the Bible is corrupt, and the passages about Mohammad have been removed. Be patient, be kind, and continue to move forward as God leads.