Musnad Ahmad 830:126

Mu'ammal narrated to us, Hammad bin Zayd narrated to us, 'Ali bin Zayd narrated to us, from al-Hasan, from Abu Bakrah, who said: While the Messenger of Allah (peace and blessings of Allah be upon him) was delivering a sermon one day, al-Hasan bin 'Ali came and climbed up to him on the pulpit. The Prophet (peace and blessings of Allah be upon him) embraced him, wiped his head, and said: "This son of mine is a sayyid (leader), and perhaps Allah will reconcile through his hands two great groups of the Muslims."