Aisha bint Abi Bakr · The Book on Sacrifices

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."

"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.

A Marfu' narration (from the Prophet (ﷺ)), saying: "A crippled animal whose limp is obvious is not to be slaughtered as sacrifice, nor an animal with a bad eye whose blindness is obvious, nor a sick animal whose sickness is obvious, nor an emaciated animal that has no marrow (in its bones)."