Which event from Muhammad's life happened first?

The marriage to Khadijah is the event that happened first in Muhammad's life among the choices listed. Khadijah was a wealthy widow who employed Muhammad as a trader. Their marriage occurred when he was about 25 years old, before he received any revelations or began his prophetic mission.

The first revelation from Angel Gabriel took place when Muhammad was approximately 40 years old, marking the commencement of his role as a prophet. The migration to Medina, also known as the Hijra, happened later in his life, in 622 CE, as did his death, which occurred in 632 CE. Thus, the correct answer highlights an important early event that set the foundation for Muhammad's later religious and social influence within the Islamic tradition.