The evidence is that Muhammad had significant knowledge of Judaism and the Old Testament. The evidence further says that Muhammad had very limited knowledge of the New Testament, as much of what he said seems to fit more of things from the false/corrupt “gospels” such as Thomas than the New Testament, such as the false stories about the supposed miracles that the baby Jesus did. It is quite clear that Muhammad said things that he learned from the Jews, such as the stories of Abraham, Moses and David. It is not at all surprising that things said in the Qur’an are similar to what is found in the Hebrew Bible. Honestly, I do not see why a Christian has to explain this. This is exactly what one would expect.