Book 43, Hadith 38

It was narrated that Jundab bin Sufyan said:"We slaughtered the sacrifice with the Messenger of Allah on day, and the people slaughtered their sacrifices before the prayer. When he finished (the prayer) the Prophet saw that they had slaughtered their sacrifices before the prayer. He said: "Whoever slaughtered his sacrifice before the prayer, let him slaughter another in its place, and whoever did not slaughter his sacrifice until we had prayed, let him slaughter it in the name of Allah, The Mighty and Sublime," (Sahih)