Mishkat al-Masabih 4463
‘Abdallah b. Ja'far said:
The Prophet waited three days before visiting the family of Ja'far (Ja'far b. Abu Talib was killed at Mu'ta in the year 7 A.H). He said, “Do not weep for my brother after today,” and then said, “Call my brother’s children to me.” When we had been brought like a number of chickens he said, “Call me a barber,” and then ordered him to shave our heads.

Abu Dawud and Nasa’i transmitted it.
وَعَن عبدِ الله بن جَعْفَرٍ: أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَمْهَلَ آلَ جَعْفَرٍ ثَلَاثًا ثُمَّ أَتَاهُمْ فَقَالَ: «لَا تَبْكُوا عَلَى أَخِي بَعْدِ الْيَوْمِ» . ثُمَّ قَالَ: «ادْعُوا لِي بَنِي أَخِي» . فَجِيءَ بِنَا كَأَنَّا أَفْرُخٌ فَقَالَ: «ادْعُوا لِي الْحَلَّاقَ» فَأَمَرَهُ فَحَلَقَ رؤوسنا. رَوَاهُ أَبُو دَاوُد وَالنَّسَائِيّ