The Islamic claim to supersede Judaism and Christianity is embodied in the theological assertion that the office of prophecy is hereditary but that the line of descent ends with Muhammad, who is the seal, or last, of the prophets.

While Muhammad had no natural sons who reached the age of maturity, he is said to have adopted a man named Zayd, and mutual rights of inheritance were created between the two. Zayd b. Muhammad, also known as the Beloved of the Messenger of God, was the first adult male to become a Muslim and the only Muslim apart from Muhammad to be named in the Qur'an. But if...

Although Muḥammad had no natural sons who reached the age of maturity, Islamic sources report that he adopted a man named Zayd shortly before receiving his first revelation. This "son of Muḥammad" was the Prophet's heir for the next fifteen or twenty years. He was the first adult male to become a Muslim and the only Muslim apart from Muḥammad whose name is mentioned in the Qur'an. Eventually, Muḥammad would repudiate Zayd as his son, abolish the institution of adoption, and send Zayd to certain death on a battlefield in southern Jordan.

Curiously, Zayd has...