Sahih Bukhari Volume 007, Book 068, Hadith Number 470.
Narrated By Al-Bara' : One day Allah's Apostle offered the 'Id prayer and said, "Whoever offers our prayer and faces our Qibla should not slaughter the sacrifice till he finishes the 'Id prayer." Abu Burda bin Niyar got up and said, "O Allah's Apostle! I have already done it. The Prophet said, "That is something you have done before its due time." Abu Burda said, "I have a Jadha'a which is better than two old sheep; shall I slaughter it?" The Prophet said, "Yes, but it will not be sufficient for anyone after you."