Bukhari

Narrated Anas: The Prophet said, "Whoever slaughtered the sacrifice before the `Id prayer, should repeat it (slaughter another one)." A man said "This is the day on which meat is desired." Then he mentioned the need of his neighbors (for meat) and the Prophet seemed to accept his excuse. The man said, "I have a Jadha'a which is to me better than two sheep." The Prophet allowed him (to slaughter it as a sacrifice). But I do not know whether this permission was general for all Muslims or not. The Prophet then went towards two rams and slaughtered them, and the people went towards their sheep and slaughtered them.

Narrated Jundab bin Sufyan Al-Bajali: I witnessed the Prophet on the Day of Nahr. He said, "Whoever slaughtered the sacrifice before offering the `Id prayer, should slaughter another sacrifice in its place; and whoever has not slaughtered their sacrifice yet, should slaughter now."

Narrated 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."