Musnad Ahmad 31:162

Yazid narrated to us, Shu'bah informed me, from Qays ibn Muslim, from Tariq ibn Shihab, who said: Marwan delivered the sermon before the prayer on the day of Eid. A man stood up and said: "The prayer used to be before the sermon." He [Marwan] said: "You see that, O Abu so-and-so?" Then Abu Sa'id al-Khudri stood up and said: "As for this man, he has fulfilled what was upon him. I heard the Messenger of Allah (peace and blessings of Allah be upon him) say: 'Whoever among you sees an evil, let him change it with his hand; if he cannot, then with his tongue; and if he cannot, then with his heart, and that is the weakest of faith.'"