Changing what is wrong

On the authority of Abu Sa'id al-Khudri (may Allah be pleased with him), who heard the Messenger of Allah (may Allah bless him and grant him peace) say: "Whoever of you sees something wrong, 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."

Related by Muslim.

[Muslim 49]