I heard the Messenger of Allah (saws) say, “Whosoever of you sees an evil, let him change it with his hand; and if he is not able to do so, then [let him change it] with his tongue; and if he is not able to do so, then with his heart — and that is the weakest of faith.” [Muslim]

Messenger of Allah (PBUH) said, "Whoever amongst you sees an evil, he must change it with his hand; if he is unable to do so, then with his tongue; and if he is unable to do so, then with his heart; and that is the weakest form of Faith".

[Muslim].

It was Marwan who initiated (the practice) of delivering khutbah (address) before the prayer on the 'Id day. A man stood up and said: Prayer should precede khutbah. He (Marwan) remarked, This (practice) has been done away with. Upon this Abu Sa'id remarked: This man has performed (his duty) laid on him. I heard the Messenger of Allah as saying: He who amongst you sees something abominable should modify it with the help of his hand; and if he has not strength enough to do it, then he should do it with his tongue, and if he has not strength enough to do it, (even) then he should (abhor it) from his heart, and that is the least of faith.

“Marwan brought out the pulpit on the day of ‘Eid, and he started with the sermon before the prayer. A man said: ‘O Marwan, you have gone against the Sunnah. You have brought out the pulpit on this day, and it was not brought out before, and you have started with the sermon before the prayer, and this was not done before.’ Abu Sa’eed said: ‘As for this man, he has done his duty. I heard the Messenger of Allah (saw) say: ‘Whoever among you sees an evil action and can change it with his hand (by taking action), let him change it with his hand. If he cannot do that, then with his tongue (by speaking out); and if he cannot do that, then with his heart (by hating it and feeling that it is wrong), and that is the weakest of faith.’”