Musnad Ahmad 27:196

Yahya narrated to us, from Ibn Jurayj, Nafi’ informed me, from Ibn ‘Umar, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "None of you shall eat from his sacrificial animal beyond three days." And ‘Abdullah, when the sun set on the third day, would not eat from the meat of his sacrificial offering.