Now, there may have been some Jews around that had practices similar to the 1st century Sadducees at the time of Mohammed, but they were not "Sadducees".
According to Islamic tradition, Muhammad received religious instruction from Waraqa ibn Nawfal, a Christian relative of his wife Khadija, following his first revelation.
Waraqa, described as a Christian who had studied the scriptures of the Torah and the Gospel, recognized Muhammad as a prophet and confirmed the divine nature of his message.
This encounter is reported in classical Islamic biographies, such as those by A. Guillaume, which state that Khadija took Muhammad to Waraqa after the initial revelation, and Waraqa affirmed that the revelation was from God.
Beyond Waraqa, some sources suggest that Muhammad may have learned about Christianity through everyday interactions with Christians in Mecca, including slaves and merchants, rather than formal instruction.
For instance, a narration cited in Islamic sources mentions that Muhammad often sat with a Christian slave named Jabr, and some accounts suggest that Jabr was a significant source of knowledge about Christianity for Muhammad.
However, critics argue that the Quran’s portrayal of Christian doctrine contains inaccuracies, such as misrepresentations of the Trinity and the claim that Mary was the sister of Aaron, which they interpret as evidence of limited or flawed understanding.