Abd al-Rahman bin Abi Awf (may Allah have mercy on him) said: Amr bin al-As and Abu al-A'war al-Sulami said to Mu'awiyah: Sayyiduna Hasan bin Ali (may Allah be pleased with them both) is a man slow of speech. Sayyiduna Mu'awiyah (may Allah be pleased with him) said: Do not say that, for the Messenger of Allah (peace and blessings be upon him) put his saliva into his mouth, and one into whose mouth the Messenger of Allah (peace and blessings be upon him) has put his saliva cannot be slow of speech. Then Sayyiduna Hasan bin Ali (may Allah be pleased with him) said: "As for you, O Amr, two men disputed over you, so see which of them is your father. And as for you, O Abu al-A'war, the Messenger of Allah (peace and blessings be upon him) cursed Ri'l, Dhakwan and Amr bin Sufyan."
Hadith Referenceالمعجم الكبير للطبراني / باب الحاء / 2686