Musannaf Ibn Abi Shayba 37:213

Abu Mu'awiyah narrated to us, from al-A'mash, from Habib, from Hudhayl ibn Shurahbil, who said: Mu'awiyah addressed them and said: "O people, you came and pledged allegiance to me willingly. Even if you had pledged allegiance to a mutilated Abyssinian slave, I would have come to pledge allegiance to him along with you." When he descended from the pulpit, 'Amr ibn al-'As said to him: "Do you know what you have brought forth today? You claimed that the people pledged allegiance to you willingly, and that if they had pledged allegiance to a mutilated Abyssinian slave, you would have come to pledge allegiance to him along with them." He said: So he regretted it, and he returned to the pulpit and said: "O people, was there anyone more entitled to this matter than me? And is there anyone more entitled to this matter than me?" He said: And Ibn 'Umar was sitting. He said: Ibn 'Umar said: "I intended to say: 'More entitled to this matter than you is the one who struck you and your father for the sake of Islam.' Then I feared that my word would cause corruption, and I remembered what Allah has prepared in the Gardens [of Paradise], so that made what I was going to say easy for me."