Musnad Ahmad 1153:1522

'Abd al-Rahman narrated to us, from Sufyan, from 'Abd al-Rahman ibn 'Abis, from his father, who said: I entered upon 'A'ishah and said to her: "Did the Messenger of Allah, may Allah bless him and grant him peace, forbid the meat of the sacrificial animals after three [days]?" She said: "Yes. A hardship befell the people, and the Messenger of Allah, may Allah bless him and grant him peace, wanted the rich to feed the poor. Then, I have indeed seen the family of Muhammad, may Allah bless him and grant him peace, eating the trotters after fifteen [days]." I said to her: "Why was that?" He said: So she laughed and said: "The family of Muhammad did not eat their fill of bread with condiment for three days until he joined Allah, the Mighty and Majestic."