I heard the Messenger of Allah ﷺ say, "Whoever among you sees something wrong, let him change it with his hand. If he is unable, then with his tongue. If he is unable, then with his heart, and that is the weakest level of faith."
سمعت رسول الله ﷺ يقول: من رأى منكم منكرا فليغيره بيده، فإن لم يستطع فبلسانه، فإن لم يستطع فبقلبه، وذلك أضعف الإيمان.
Muslim narrated it in the Book of Faith (49) through several routes from Qays bin Muslim, from Tariq bin Shihab, who said, "The first to begin the sermon before the prayer on the day of Eid was Marwan. A man stood up to him and said, 'The prayer comes before the sermon.' He said, 'What used to be done there has been abandoned.' Abu Saeed then said, 'As for this man, he has fulfilled what was required of him. I heard the Messenger of Allah ﷺ say,'" and then he related the hadith.