Whenever we try to compare or distinguish between Christianity and Islam, we must remember that there is no real religious relationship between these two religions. In fact, Islam seeks to legitimize itself in the eyes of the world by claiming to recognize Isaac, Jacob, Joseph, Moses, David, Solomon, and many other Old Testament prophets as well as Isa [Jesus] as prophets. But since there is a clear dividing line between Ishmael and Isaac, after Abraham all the above-mentioned prophets are only of the lineage of Isaac, so they can never be prophets of Islam.
Above all, then, the Bible nowhere teachs that the Arabs are biological descendants of Ishmael, as one is commonly led to believe, just as many of the current missionary agencies among the Muslims are trying to consider a biological brotherhood, completely non-existent, between the descendants of Ishmael and the Arabs as desired by Islam.
Rr. Emmanuel Atif. (Ex musulmano – Esperto teologia islamica – Pastore in Bangladesh)