Abu Sa'eed said:"I heard the Messenger of Allah [SAW] say: 'Whoever among you sees an evil, let him change it with his hand; if he cannot, then with his tongue; if he cannot, then with his heart- and that is the weakest of Faith.'"
أَخْبَرَنَا مُحَمَّدُ بْنُ بَشَّارٍ، قَالَ حَدَّثَنَا عَبْدُ الرَّحْمَنِ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ قَيْسِ بْنِ مُسْلِمٍ، عَنْ طَارِقِ بْنِ شِهَابٍ، قَالَ قَالَ أَبُو سَعِيدٍ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " مَنْ رَأَى مُنْكَرًا فَلْيُغَيِّرْهُ بِيَدِهِ فَإِنْ لَمْ يَسْتَطِعْ فَبِلِسَانِهِ فَإِنْ لَمْ يَسْتَطِعْ فَبِقَلْبِهِ وَذَلِكَ أَضْعَفُ الإِيمَانِ " .
Nesai
The Book Of Faith and its Signs • Hadith 5008