"The Messenger of Allah stayed away from the family of Ja'far (when he died) for three days, then he came to them, and said: 'Do not weep for my brother after today.' Then he said: 'Call my brother's sons to me.' We were brought like little chicks, and he said: 'Call the barber for me.' Then he ordered that our heads be shaved."
Sunan an-Nasa'i Book 48, Hadith 188