Musnad Ahmad 830:143

'Affan narrated to us, Mubarak bin Fudalah narrated to us, from al-Hasan, Abu Bakrah informed me that the Messenger of Allah (ﷺ) was praying. When he prostrated, al-Hasan would jump onto his back and his neck. So the Messenger of Allah (ﷺ) would lift him up gently so that he would not fall. He said: He did that more than once. When he finished his prayer, they said: "O Messenger of Allah, we saw you do something with al-Hasan that we have not seen you do before." He said: "He is my sweet basil of the world, and this son of mine is a leader, and perhaps Allah will reconcile through him between two groups of the Muslims."