Yonus bin Yazid bin Abi al-Nijad يونس بن يزيد بن أبي النجاد · 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."

That the Messenger of Allah (ﷺ) said: "The boy is mortgaged by his 'Aqiqah; slaughtering should be done for him on the seventh day, he should be given a name, and his head should be shaved."