Imamah (Shia doctrine)
It is forbidden for the Divine Leader not to be from the family of Muhammad.[citation needed] According to Ali al-Ridha, since it is obligatory to obey him, there should be a sign to clearly indicate the Divine Leader. That sign is his well-known ties of kinship with Muhammad and his clear appointment so that the people could distinguish him from others, and be clearly guided toward him. Otherwise others are nobler than Muhammad's offspring and they are to be followed and obeyed; and the offspring of Muhammad are obedient and subject to the offspring of Muhammad’s enemies such as Abi Jahl or Ibn Abi Ma’eet.[original research?] However, Muhammad is much nobler than others to be in charge and to be obeyed. Moreover, once the prophethood of Muhammad is testified they would obey him, no one would hesitate to follow his offspring and this would not be hard for anyone. While to follow the offspring of the corrupted families is difficult.[original research?] And that is maybe why the basic characteristic of Muhammad and other prophets was their nobility.[original research?] For none of them, it is said, were originated from a disgraced family.[citation needed] It is believed that all Muhammad's ancestors up to Adam were true Muslims. [a][citation needed] Jesus was also from a pious family, as it is mentioned in Quran that after his birth, people said to Mary: O sister of Aaron, your father was not a man of evil, nor was your mother unchaste."[b][improper synthesis?]

Q: What is the sign that indicates the Divine Leader?
his well-known ties of kinship with Muhammad