Sahih Bukhari Volume 007, Book 068, Hadith Number 463.
Narrated By Al-Bara' bin 'Azib : An uncle of mine called Abu Burda, slaughtered his sacrifice before the 'Id prayer. So Allah's Apostle said to him, "Your (slaughtered) sheep was just mutton (not a sacrifice)." Abu Burda said, "O Allah's Apostle! I have got a domestic kid." The Prophet said, "Slaughter it (as a sacrifice) but it will not be permissible for anybody other than you" The Prophet added, "Whoever slaughtered his sacrifice before the ('Id) prayer, he only slaughtered for himself, and whoever slaughtered it after the prayer, he offered his sacrifice properly and followed the tradition of the Muslims."