Musnad Ahmad 27:1077

Hajjaj ibn Muhammad narrated to us, from Ibn Jurayj, Nafi’ informed me, that Ibn ‘Umar used to say: 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." He said: And ‘Abdullah, when the sun set on the third day, would not eat from the meat of his sacrificial offering.