Musannaf Ibn Abi Shayba 37:264

Yahya ibn Adam narrated to us, he said: Ibn ‘Uyaynah narrated to us, from Mujalid, from al-Sha’bi, who said: When the peace treaty took place between al-Hasan ibn ‘Ali and Mu’awiyah, al-Hasan wanted to depart for Medina. Mu’awiyah said to him, "You shall not leave until you address the people." Al-Sha’bi said: So I heard him on the pulpit. He praised Allah and extolled Him, then said: "The most intelligent of the intelligent is the God-fearing, and the most incapable of the incapable is the wicked. This matter, which I and Mu’awiyah differed over—until it was mine and I left it for Mu’awiyah—was a right that he did not see as more rightful for me than himself. I only did this to spare your blood. And I do not know, perhaps it is a trial for you and an enjoyment for a time." Then he descended.