Tariq bin Shihab reported,

The first person to deliver the sermon before the prayer was Marwan. A man stood up and said to Marwan, "You have gone against the Sunnah."Marwan replied, "So-and-so, that practice has been abandoned."Abu Saeed said, "As for this man, he has fulfilled his duty. I heard the Messenger of Allah ﷺ say, 'Whoever among you sees an evil, let him change it with his hand. If he is unable, then with his tongue. And if he is unable, then with his heart, and that is the weakest of faith.'"

Tirmidhi 2172

Sahih

حدثنا بندار حدثنا عبد الرحمن بن مهدي حدثنا سفيان عن قيس بن مسلم

عن طارق بن شهاب قال

أول من قدم الخطبة قبل الصلاة مروان فقام رجل فقال لمروان خالفت السنة فقال يا فلان ترك ما هنالك فقال أبو سعيد أما هذا فقد قضى ما عليه سمعت رسول الله ﷺ يقول من رأى منكرا فلينكره بيده ومن لم يستطع فبلسانه ومن لم يستطع فبقلبه وذلك أضعف الإيمان

الترمذي 2172صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami Tirmidhi
Book
Tribulations
Chapter
Changing evil by the hand, the tongue, or the heart
Numbering
Darussalam 2172
Tirmidhi 2172