From 613 to 619 CE, the Islamic prophet Muhammad gathered in his hometown of Mecca a small following of those who embraced his message of Islam and thus became Muslims. The first person who professed Islam was his wife, Khadija bint Khuwaylid. The identity of the second male Muslim, after Muhammad himself, is nevertheless disputed largely along sectarian lines, as Shia and some Sunni sources identify him as the first Shia imam Ali ibn Abi Talib, a child at the time, who grew up in the household of his uncle, Muhammad. Other sources report that the first male convert was Abu Bakr, who later succeeded Muhammad as the first Sunni caliph, or Muhammad's foster son, Zayd ibn Haritha. While it is difficult to establish the chronological order of early conversions, the identities of early Muslims are known with some certainty.