Musnad Ahmad 830:100

'Abd al-Razzaq narrated to us, Ma'mar informed us, he who heard al-Hasan narrated to me, speaking about Abu Bakrah, who said: The Prophet, peace and blessings of Allah be upon him, was speaking to us one day while al-Hasan ibn 'Ali was in his lap. He would turn to his companions and speak to them, then he would turn to al-Hasan and kiss him. Then he said: "Indeed, this son of mine is a sayyid (leader/master). If he lives, he will reconcile between two groups of the Muslims."