Some of the first Christians to encounter Muslims in the 8th and 9th centuries did not view Islam as a new religion. Rather, people like John of Damascus, in his work, De Haeresibus, believed Islam was simply an old-style Christian heresy dressed in new garb.

One codex of John's book describes his belief that Jews, Arians, and Nestorians were the cause behind Muhammad’s religion. From the Arians, Muhammad learned that Jesus was created and not eternal. From the Nestorians, Muhammad learned to place a stress on Christ’s humanity.

According to Muhammad’s eighth-century biography, the Sīrat, by hagiographer Muhammad ibn Ishāq, Christian monk Sergius-Bahira recognized a prophetic mark on Muhammad’s body and related the foretelling of his ascendency from earlier Scriptures. This short story involving Bahira was likely invented by Muslims to answer the Christian charge that Muhammad was unannounced and, thus, a false prophet. The apologetic legend was designed to give a Christian approval of Muhammad’s prophethood.

But according to John of Damascus, the monk Bahira was actually an Arian heretic who misled the Arab people. Yet, legend of Muhammad’s encounter with Bahira is also found in both Syrian and Arab Christian circles during the 9th century. Indeed, both Monophysite and Nestorian Christians had a copy of a different version of the legend, which claimed that Bahira was the actual author of the Qur’an.

One purpose of containing such a legend was to demonstrate that the Qur’an originated from Christianity and not from Muhammad. In this version, Bahira claims that Muhammad had trouble differentiating between the polytheists and the Christians. In sura 4:157, Bahira did not intend to say that Jesus never died on the cross. Instead, he meant only that Jesus did not die in his divine nature.

This Christian version of the Muhammad legend presents Islam as a mistaken form of Christianity. Here, Bahira is presented as a fugitive monk from the Nestorian tradition, who attempted to convert the Arab polytheists by contextualizing Christianity for Arab culture. Originally, the Qur’an contained a pure gospel message prior to Jewish converts distorting the record and making Islam what it is known today. Bahira even gave himself the name “Nestorius,” in order to promote Nestorian Christology. This may account for another Muslim legend of Muhammad meeting a monk on his way to Syria named Nasṭûr (Nestorius?), who also declared Muhammad’s future prophethood.

According to some scholars, the Christian legend of Bahira likely originated from Monophysite Christians in order to blame the Nestorians for the rise of Islam.