It is narrated from Sayyiduna Abu Burdah (may Allah be pleased with him) that once I performed the Eid prayer with the Prophet (peace and blessings of Allah be upon him). Behind me, my wife caught the sacrificial animal, slaughtered it, and prepared its meat. When I finished the prayer and reached home, she brought the food items. I asked her: Where did this come from? She said: We slaughtered the sacrificial animal and prepared food for you so that when you return, you can have breakfast. I said to her that I fear this way of doing it may not be correct. So I went to the Prophet (peace and blessings of Allah be upon him) and narrated the whole incident. The Prophet (peace and blessings of Allah be upon him) said: The sacrifice has not been done. Whoever slaughters the animal before we finish our prayer, his sacrifice is not valid. Therefore, you should offer the sacrifice again. When I searched for a year-old animal, I could not find one. So I went again and said: O Messenger of Allah (peace and blessings of Allah be upon him)! By Allah, I have searched for a musinnah (a year-old animal), but I am unable to find one. The Prophet (peace and blessings of Allah be upon him) said: Then look for a six-month-old lamb and sacrifice that. Or this was a concession from the Prophet (peace and blessings of Allah be upon him) for him.
Hadith Referenceمسند احمد / مسند المدنيين رضي الله عنهم اجمعين / 16490
Hadith Gradingحکم دارالسلام:إسناده حسن إن صح سماع بشير بن يسار من أبى بردة