Imam Sadiq (peace be upon him): Isa ibn Dawud al-Najjar said: Imam Kazim (peace be upon him) narrated to me and said: "One day I was sitting with my father, until a man came and stood before him and said: 'Is the splitter of knowledge, whose leader is Muhammad ibn Ali (peace be upon him), among you?' It was said: 'Yes.' He then sat for a long while, then rose before the Imam and said: 'O son of the Messenger of Allah (peace be upon him and his family)! Inform me about this verse of Allah concerning the story of Zakariyya (peace be upon him): وَ إِنِّی خِفْتُ الْمَوَالِیَ مِن وَرَائِی وَ کَانَتِ امْرَأَتِی عَاقِرًا [And surely I fear my cousins after me, and my wife is barren].' He said: 'Yes, the mawali are the children of the uncle, and Allah loved to bestow upon him a guardian from his own loins. That was because when Zakariyya became aware of the merit of Muhammad (peace be upon him and his family), he said: "O my Lord, did You not honour Muhammad (peace be upon him and his family) and exalt him and raise his mention until You placed his name alongside Your own name? Now, O my Master, what would it be if You granted him offspring from his loins in whom prophethood would be?" Allah said: "O Zakariyya! I have done that for Muhammad (peace be upon him and his family), and there is no prophethood after him, for he is the Seal of the Prophets. But I have entrusted the Imamate after him to his cousin and brother Ali ibn Abi Talib (peace be upon him), and I have transferred the offspring from the loins of Ali (peace be upon him) into the womb of Fatima (peace be upon her), and I brought them into being from [the lineage of] one another, and from him I brought forth my Imams (peace be upon them) who are my proofs among my servants. And indeed I shall bring forth from your loins a son who will inherit from you and inherit from the family of Yaqub." So Allah bestowed upon him Yahya (peace be upon him).'"