Imam Kazim (peace be upon him): Muhammad ibn Mahmud, with his chain, narrates from Imam Kazim (peace be upon him) that he said: "I came before Harun al-Rashid. He said to me, 'How is it that you say you are the children of the Prophet (peace be upon him and his family), while the Prophet (peace be upon him and his family) had no progeny? For progeny is through the male child, not the female child, and you are the children of a daughter, and a daughter has no progeny.' I said, 'By the right of kinship and by the grave [of the Prophet (peace be upon him and his family)] and the one who is in it, I ask you to excuse me from this question.' He said, 'No, unless you inform me of your proof regarding it, O son of Ali (peace be upon him)! And thus it has been reported to me that you, O Musa, are their chief and the Imam of their time, and I will not excuse you from anything I ask you about until you bring me a proof from the Book of Allah the Exalted regarding it. For you, the group of the children of Ali (peace be upon him), claim that nothing of the Qur'an — neither an alif nor a waw — is missed by you but that its interpretation is with you, and you cite as proof this word of Allah the Mighty and Majestic: ما فَرَّطْنا فِی الْکِتابِ مِنْ شَیْءٍ [We have not neglected anything in the Book], and you consider yourselves independent of the opinion of the scholars and their analogy.' I said, 'Do you permit me to answer?' He said, 'Bring [your answer] forth.' I said, 'أَعُوذُ بِاللهِ مِنَ الشَّیْطَانِ الرَّجِیمِ، بِسْمِ اللهِ الرَّحْمنِ الرَّحِیمِ، وَ مِنْ ذُرِّیَّتِهِ داوُدَ وَ سُلَیْمانَ وَ أَیُّوبَ وَ یُوسُفَ وَ موسی وَ هارُونَ وَ کَذلِکَ نَجْزِی المُحْسِنِینَ* وَ زَکَرِیَّا وَ یَحْیی وَ عِیسی [I seek refuge with Allah from the accursed Satan. In the name of Allah, the Most Merciful, the Most Compassionate. And of his descendants, Dawud and Sulayman and Ayyub and Yusuf and Musa and Harun; and thus do We reward those who do good. And Zakariyya and Yahya and Isa]; O Commander of the Believers! Who is the father of Isa (peace be upon him)?' He said, 'Isa (peace be upon him) has no father.' I said, 'We attached him to the descendants of the prophets (peace be upon them) through the path of Maryam (peace be upon her), and likewise we are attached to the descendants of the Prophet (peace be upon him and his family) through our mother Fatima (peace be upon her).'"