Muslims sometimes claim that the coming of Muhammad is prophesied in John 14 under the name of the Helper. I doubt this; there is not a lot of similarity between the actual work of Muhammad and how the Helper is described here, so I must contend that the Helper is the Holy Spirit, the third Person of the Trinity. But there is another section of the New Testament that seems to be relevant to the phenomenon of Islam.
I refer you to Galatians 4:21-31. Here is part of it:
“For it is written that Abraham had two sons, one by a slave woman and one by a free woman. But the son of the slave was born according to the flesh, while the son of the free woman was born through promise. Now this may be interpreted allegorically: these women are two covenants. One is from Mount Sinai, bearing children for slavery; she is Hagar. Now Hagar is Mount Sinai in Arabia; she corresponds to the present Jerusalem, for she is in slavery with her children. But the Jerusalem above is free, and she is our mother.”
Most Muslims today (e.g., Persians, Turks, Indians, South Asians) do not claim descent from Hagar and Ishmael, but the founders did. And they imposed their own language as the sacred language of the faith, so that the Quran in any other tongue is a mere interpretation; and they even altered the Genesis story to make it that Abraham nearly sacrificed Ishmael, not Isaac, and this is the basis of one of their major festivals.
Galatians is not quite a prophecy. But it did happen that the descendants of Hagar in fact founded a faith to bring in God’s kingdom ‘after the flesh’ or by human means, not according to the promise. And now, once again, they are one of the chief challenges to the Church as well as to post-Christian civilization.