Whenever the Messenger of Allah ﷺ intended to offer a sacrifice, he would buy two large, fat, horned, white rams that had been castrated. He would slaughter one of them on behalf of his community, for whoever bore witness that Allah is One and bore witness that he had delivered the message, and he would slaughter the other on behalf of Muhammad and the family of Muhammad ﷺ.
حدثنا محمد بن يحيى حدثنا عبد الرزاق أنبأنا سفيان الثوري عن عبد الله بن محمد بن عقيل عن أبي سلمة
أن رسول الله ﷺ كان إذا أراد أن يضحي اشترى كبشين عظيمين سمينين أقرنين أملحين موجوءين فذبح أحدهما عن أمته لمن شهد لله بالتوحيد وشهد له بالبلاغ وذبح الآخر عن محمد وعن آل محمد ﷺ
[Hasan] Ahmad recorded it (6/225) from Abdul-Razzaq with this wording, and Busiri graded it hasan. Thawri narrated it using "an," as already discussed under hadith no. 162. It has a corroborating witness in Ahmad (6/391, 392), and its chain of transmission is hasan. Likewise, Waki narrated it from Sufyan (Ahmad 6/136).