I saw Ali sacrificing two rams, so I asked him, "What is this?"He replied, "The Messenger of Allah ﷺ instructed me to offer a sacrifice on his behalf, so I am sacrificing on his behalf."
حدثنا عثمان بن أبي شيبة حدثنا شريك عن أبي الحسناء عن الحكم
رأيت عليا يضحي بكبشين فقلت له ما هذا فقال إن رسول الله ﷺ أوصاني أن أضحي عنه فأنا أضحي عنه
Its isnad is daif. Tirmidhi narrated it in the Book of Udhiya, chapter on what has been reported about udhiya on behalf of the deceased, hadith no. 1495, from the hadith of Sharik the judge, with this wording, and he said, "Gharib."Sharik and Hakam bin Utayba both narrated using "an" (indicating a possible break in the chain), and Abul-Hasna is unknown, and he is not the same as Hasan bin Hakam Nakhai. This confusion occurred with Hakim in volume 4, where he graded it sahih, and Dhahabi agreed with him.