That 'Ali used to slaughter two male sheep, one for the Prophet (ﷺ) and the other for himself. When this was mentioned to him, he said: "He ordered me to" - meaning the Prophet (ﷺ) - "So I will never leave it."
Jami` at-Tirmidhi Book 19, Hadith 3
← Previous Hadith "The Messenger of Allah (ﷺ) slaughtered two horned male sheep which were mostly white. He slaughtered them with his hand and mentioned Allah's Name, and he said 'Allahu Akbar', and put his foot on their side."

Jami` at-Tirmidhi Book 19, Hadith 2 Next Hadith → "The Messenger of Allah (ﷺ) slaughtered a horned male ram of fine pedigree, (around) his mouth was black, and his legs were black, and (around) his eyes was black.

Jami` at-Tirmidhi Book 19, Hadith 4