Sayyiduna al-Bara' bin Azib (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) delivered a sermon on the day of Eid al-Adha after the prayer and said: "Whoever prays as we pray and sacrifices as we sacrifice, his sacrifice is valid; and whoever sacrifices before the prayer, his goat is a goat for meat, and it is not a sacrifice for him." Abu Burdah (may Allah be pleased with him), who was the maternal uncle of al-Bara' bin Azib (may Allah be pleased with him), said: O Messenger of Allah, I slaughtered my goat before the prayer, for I knew that today is a day of eating and drinking, and I wanted my goat to be the first thing slaughtered in my house; so I slaughtered it and ate of its meat before coming to the prayer. He (peace and blessings be upon him) said: "Your goat is a goat for meat." He said: O Messenger of Allah, I have a young female goat, a jadha'ah. Will it suffice for me, given that it is dearer to me than two goats? He (peace and blessings be upon him) said: "Yes, but it will not suffice for anyone after you."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة العيدين / 6164