An-Nawawi's 40 Hadith 34
الأربعون النووية#34Not gradedعَنْ أَبِي سَعِيدٍ الْخُدْرِيّ رَضِيَ اللهُ عَنْهُ قَالَ سَمِعْت رَسُولَ اللَّهِ صلى الله عليه و سلم يَقُولُ: مَنْ رَأَى مِنْكُمْ مُنْكَرًا فَلْيُغَيِّرْهُ بِيَدِهِ، فَإِنْ لَمْ يَسْتَطِعْ فَبِلِسَانِهِ، فَإِنْ لَمْ يَسْتَطِعْ فَبِقَلْبِهِ، وَذَلِكَ أَضْعَفُ الْإِيمَانِ . [رَوَاهُ مُسْلِمٌ]
On the authority of Abu Sa`eed al-Khudree (may Allah be pleased with him) who said: I heard the Messenger of Allah (ﷺ) 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]
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Our source carries no per-scholar grade for this narration. Please verify on Sunnah.com or with a qualified scholar before relying on it.
In-book reference: 1:34