I was with 'Ali b. Abi Talib on the occasion of the 'Id day. He started with the 'Id prayer before delivering the sermon, and said: Messenger of Allah ﷺ forbade us to eat the flesh of our sacrificial animals beyond three days.
وَقَالَ إِنَّ رَسُولَ اللَّهِ ﷺ نَهَانَا أَنْ نَأْكُلَ مِنْ لُحُومِ نُسُكِنَا بَعْدَ ثَلاَثٍ