رِيَاضُ الصَّالِحِينَ
Riyad as-Salihin 184
The Book of Miscellany
Enjoining Good and forbidding Evil
فالأول: عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ رَضِيَ اللَّه عَنْهُ قَالَ: سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّه عَلَيْهِ وَسَلَّمَ يَقُولُ: مَنْ رَأَى مِنْكُمْ مُنْكَرًا فَلْيُغَيِّرْهُ بِيَدِهِ ، فَإِنْ لَمْ يَسْتَطِعْ فَبِلِسَانِهِ، فَإِنْ لَمْ يَسْتَطِعْ فَبِقَلْبِهِ وَذَلِكَ أَضْعَفُ الْإِيمَانِ ((رَوَاهُ مُسْلِمٌ)).
Abu Sa'id Al-Khudri (May Allah be pleased with him) reported: Messenger of Allah (ﷺ) 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].
Riyad as-Salihin, 184