Musnad Ahmad 1242:0

Mu'awiyah ibn Hudayj narrated: I entered upon Mu'awiyah ibn Abi Sufyan and said, "O Commander of the Faithful, I heard the Messenger of Allah (ﷺ) say: 'If you pursue the faults of the people, you will corrupt them—or you will nearly corrupt them.'" Mu'awiyah said, "I heard this from the Messenger of Allah (ﷺ), and I do not doubt that it is the truth from the Messenger of Allah (ﷺ). If the people were to pursue the faults of the people, they would corrupt them."