PREVENT WRONGDOING H 238 "Go to the help of your brother even if he does wrong or is wronged. A Companion asked: 'O Messenger of Allah, praise and peace be upon him, I can help him if he is wronged, but tell me how can I help him if he does wrong?' He answered: 'Prevent him from doing what is wrong; that is helping him.'" R 238 Bukhari with a chain up to Anas who related that the Prophet, praise and peace be upon him, said this.
237- وعنه ، قَالَ : قَالَ رَسُول الله صلى الله عليه وآله وسلم : "انْصُرْ أخَاكَ ظَالماً أَوْ مَظْلُوماً" فَقَالَ رجل : يَا رَسُول اللهِ ، أنْصُرُهُ إِذَا كَانَ مَظْلُوماً ، أرَأيْتَ إنْ كَانَ ظَالِماً كَيْفَ أنْصُرُهُ ؟ قَالَ : "تحْجُزُهُ - أَوْ تمْنَعُهُ - مِنَ الظُلْمِ فَإِنَّ ذلِكَ نَصرُهُ" رواه البخاري .