According to the Koran: "God chose Adam and Noah and the family of Abraham and the family of Imran above all (His) creatures. Offspring, one from the other"(3:33-34). The word dhurriya means direct descendants, family or lineage. It occurs 32 times in the Koran in the context of the prophets, indicating that their mission was assigned to their direct descendants to carry on.

Noah was a descendant of Adam. Abraham was a descendant of Noah and Imran was descendant of Abraham through his son Isaac, who became known as Al'i Imran. Imran (Hebrew, Amram) was the father of Moses and Aaron, called Imran bin Yashar or Imran bin Qahith. Another Koranic Imran was Mary's father, called Imran bin Mathan or Matan. The two Imrans are different persons, separated by a long period of time, one thousand and eight hundred years. The line of Al'i Imran ended with Jesus.

While the descendants of Ismael, the son of Abraham, are known as Al'i Ibrahim. The Prophet of Islam is from the Al'i Ibrahim. The lineage of Al'i Ibrahim continued to Abdul Muttalib, and there got again bifurcated into Abdullah and Abu Talib. Of Abdullah came the Prophet of Islam and of Abu Talib came Ali and these two channels were re-united through Fatima, and thus the lineage of Al'i Ibrahim continued through Ali and Fatima, known as the Fatimids. The fact that Abraham's family (Al'i Ibrahim) being blessed with forever is borne out from a similar declaration found in the Old Testament (Genesis. 12:1-3; 17:1-9). The phrase dhurriatan ba'zoha min ba'z (offspring, one from the other) in the above Koranic verse indicates that the descent of Al'i Ibrahim will continue till the day of judgment.

From the time of Adam, there has been a continuous succession of the Divine Guides. Some figure Noah, Abraham, Moses, Jesus and Muhammad have combined in themselves the function of prophethood, but at no time is the earth left without the Guide (hadi) and Proof (hujja) of God. Imam Muhammad al-Bakir said, "By God! God has not left the earth, since the death of Adam, without there being on it an Imam guiding (the people) to God. He is the Proof of God to His servants and the earth will not remain without the Proof of God to his servants." (al-Kafi, 1:178). Imam Jafar Sadik also said, "Were there to remain on the earth but two men, one of them would be the Proof of God" (Ibid. 1:179). According to the Ismailis, there must be an Imam on earth in the progeny (dhurriya) of the Prophet. The office of the Imam can only pass from one to the other by legitimate succession and explicit appointment, and the earth cannot remain even a single moment without an Imam.