The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1305
This hadith has been reported by 'Auza'i with the same chain of transmitters: We used to slaughter the camel during the lifetime of the Messenger of Allah (may peace be upon him) after the 'Asr prayer, but he made no mention of:" We used to pray along with him."