This was not uncommon in those days but keep in mind that he could not read things for himself, he could only repeat what he heard. As a Christian, it seems that much of what he knew about the Bible he heard from local heretical sects. Here we see the influence of the Gospel of Thomas.
“and he shall be an apostle to the children of Israel. "Now have I come," he will say, "to you with a sign from your Lord: Out of clay will I make for you, as it were, the figure of a bird: and I will breathe into it, and it shall become, by God's leave, a bird.20 And I will heal the blind, and the leper; and by God's leave will I quicken the dead; and I will tell you what ye eat, and what ye store up in your houses! Truly in this will be a sign for you, if ye are believers.” Surah 3, “The Family of Imrhan,” verse 49To an orthodox Christian, turning clay into birds is not in the spirit of the Bible. In the Gnostic Gospel of Thomas Jesus turned some children into birds. You can see the connection. Most of his knowledge of the Christian Bible came from heretics.
There were also early heresies that denied the physical death of Jesus on the Cross. We see that in this passage.
“And for their saying, ‘Verily we have slain the Messiah, Jesus the son of Mary, an Apostle of God.’ Yet they slew him not, and they crucified him not, but they had only his likeness. And they who differed about him were in doubt concerning him: No sure knowledge had they about him, but followed only an opinion, and they did not really slay him, but God took him up to Himself. And God is Mighty, Wise!” Surah 4, “Women,” verse 157Notice that is was His “likeness” that was crucified.
Of course heresy is in the eyes of the beholder. If you are a Muslim and believe that Gabriel actually dictated this to Mohammed, that is not a problem. It would just make the Gnostics right and orthodox Christians wrong. I guess if you are a Muslim you figure the Christians are wrong anyway.
Keep in mind that Mohammed is having his visions around the year 610. By this time the Christian church had worked through the debates on Gnosticism and rejected its positions. In a sense the Muslim rejection of “Christianity” was consistent with Christianity’s rejection of these false teachings. I guess that gives us something in common.
homo unius libri