(2) باب الأُضْحِيَةِ عَنِ الْمَيِّتِ
Narrated Hanash:
I saw Ali sacrificing two rams; so I asked him: What is this? He replied. The Messenger of Allah (ﷺ) enjoined upon me to sacrifice on his behalf, so that is what I am doing.
Reference: Sunan Abi Dawud 2790
In-book reference: Book 16, Hadith 3
English translation: Book 15, Hadith 2784