I said to the Prophet ﷺ, "Your uncle, the misguided old man, has died."He said, "Go and bury your father, then do not do anything else until you come to me."So I went, buried him, and came back. He instructed me to perform a full bath, and I did so, and he prayed for me.
قلت للنبي ﷺ: إن عمك الشيخ الضال قد مات، قال: اذهب فوار أباك، ثم لا تحدثن شيئا حتى تأتيني فذهبت فواريته وجئته، فأمرني فاغتسلت، ودعا لي.
Abu Dawud (3214), Nasai (2006), Ibn Jarud (550), and Ahmad (1093) all narrated it through the hadith of Abu Ishaq, from Najiya bin Kaab, from Ali bin Abu Talib, and he mentioned it. Its isnad is hasan because of Najiya bin Kaab, for there is disagreement about him. Yahya bin Main was asked about him and said, "Salih." Abu Hatim said, "A shaykh." Ajli said, "A trustworthy man of Kufa." Ibn Hajar placed him at the level of "thiqah," but I think he does not rise above the level of "saduq." Ibn Madini criticized him, saying, "Unknown."Ibn Hajar mentioned it in "Fath" (7/195) and passed over it in silence, except that he also attributed it to Ibn Khuzayma, which is a slip on his part, for he did not attribute it to him in Ithaf Mahra (14776), so take note.Bayhaqi (1/304) transmitted from Ibn Madini that he said, "We found this hadith only among the people of Kufa." Bayhaqi said, "There is something questionable in its isnad. Abu Ishaq narrated it from Najiya, and we do not know of anyone who narrated from Najiya other than Abu Ishaq." Imam Ahmad said, "It has also been narrated through another daif route from Ali in this manner." End of quote.I say, perhaps Imam Ahmad is referring to what he narrated in his Musnad (807) from Ibrahim bin Abu Abbas, who said, Hasan bin Yazid Asamm narrated to us, he said, I heard Suddi Ismail mention it from Abu Abdul-Rahman Sulami, from Ali, and he mentioned it, adding at the end of the hadith, "So he made a supplication for me that I would not exchange for red or black camels." He said, "And whenever Ali washed a deceased person, he would then perform ghusl himself." This isnad has some weakness in it.Ibn al-Imam narrated it in Zawaid al-Musnad (1074) through another route from Hasan bin Yazid Asamm with a similar isnad, and this second isnad strengthens the first isnad which comes through the route of Najiya bin Kaab.Ibn Hajar said in "Talkhis," after attributing it to those who narrated it through the route of Abu Ishaq, "The gist of Bayhaqi's discussion is that it is daif, though the reason for its weakness is not clear. Rafii said it is an established, well-known hadith, saying so in his Amali."I say, this hadith, even though there is some discussion of it from the standpoint of transmission, nevertheless indicates an incident that undoubtedly occurred. For if Ali bin Abu Talib had not done this for his father, what else would have been required of him after his death? As for the claim that he washed Abu Talib before burying him, this has not been established, neither in a sahih hadith nor in a daif one. What is established is only that the Prophet ﷺ ordered him to perform ghusl after burying him, as a matter of cleanliness, for ghusl was only legislated in connection with washing the deceased, and it was not legislated in connection with burying him. This is why no one has held the view of performing ghusl on account of burial.