Musnad Ahmad 5:620

Muhammad ibn Ja'far narrated to us, Mu'ammar narrated to us, al-Zuhri narrated to me, from Abu 'Ubayd, the freed slave of 'Abd al-Rahman ibn 'Awf, who said: I witnessed 'Ali, who said: "I heard the Messenger of Allah, may Allah bless him and grant him peace, forbidding anyone from keeping anything of his sacrificial meat (nusuk) for more than three days."