Sahih Muslim Book 22, Hadith Number 4861.

Chapter : It was not permissible to eat the flesh of sacrificial animals beyond three days at the beginning of Islam, but this prohibition was abrogated, and now it is permissible.

Abu Sa’id al-Khudri reported Allah’s Messenger (may peace be upon him) having said: O people of Medina, do not eat the flesh of sacrificed animals beyond three days. Ibn al-Muthanni said: Three days. They (the Companions of the Holy Prophet) complained to the Messenger of Allah (may peace he upon him) that they had children and servants of theirs (to feed), whereupon he said: Eat, and feed others, and store, and make it a provision of food.