كَانُوا لَا يَتَنَاهَوْنَ عَن مُّنكَرٍ فَعَلُوهُ لَبِئْسَ مَا كَانُوا يَفْعَلُونَ
They would not forbid one another from the wrongs that they committed. Surely, evil is what they had been doing.
Agha Ali Puya Commentary
Commentary on Quran 5:79
[Pooya/Ali Commentary 5:79] The Jews did not restrain one another from evil (nahya anil munkar), therefore, they were so easily led astray. Nahya anil munkar has been prescribed by Islam. See commentary of Ali Imran : 101 to 115 (Aqa Puya's note on amr bil ma-ruf and nahya anil munkar).