Abu Sa'íd Al Khudrí (Ra) narrates: I heard Rasúlullãh (saw) saying: Anybody amongst you who sees an evil should change it with his hands; if he is unable to do so, then with his tongue; if he is unable to do this (even), then by his heart and this is the weakest form of Ímãn.

(Muslim)

Note: To change it by his heart means that one should at least consider it a vice in his heart and should supplicate for its change.