Sahih Muslim Book 022, Hadith Number 4856.
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.
Abdullah b. Waqid reported: Allah's Messenger (may peace be upon him) forbade (people) to cat the flesh of sacrificed animals beyond three days. Abdullah b. Abu Bakr said, I made a mention of that to 'Amra, whereupon she said: He has told the truth, for I heard 'Aisha say: The poor among the people of the desert come (to the towns) on the occasion of Id al-Adha during the lifetime of Allah's Messenger (may peace be upon him). Upon this Allah's Messenger (may peace be upon him) said: Retain with you (the flesh) sufficing for three (days), and whatever is left out of that give in charity. After this, they (the Muslims) said: Allah's Messenger, the people make water-skins with the (hides) of their sacrificed animals and they melt fat out of them. Thereupon he said. What the then? They said: You forbade (us) to eat the flesh of sacrificial animals beyond three (days), whereupon he said: I forbade you for those (poor persons) who flocked (to the towns on this occasion for getting meat) but now when (this situation has improved) you may eat, preserve and give -in charity.