Abu Ubayd, the freed slave of Abd al-Rahman bin Awf, heard Ali (may Allah be pleased with him) say on the day of al-Adha: "O people! The Messenger of Allah (peace and blessings be upon him) has forbidden you from eating your sacrifices after three days, so do not eat them."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19205