Musnad Ahmad 20:3

Abu Mu'awiyah narrated to us, 'Asim narrated to us, from Muwarriq al-'Ijli, from 'Abdullah ibn Ja'far, who said: "When the Messenger of Allah (peace and blessings of Allah be upon him) would return from a journey, he would be met by the children of his household." He said: "And he returned once from a journey, and I was brought forward to him, so he carried me in front of him." He said: "Then one of the two sons of Fatimah was brought, either Hasan or Husayn, and he placed him behind him." He said: "So we entered Medina, three on a beast."