5:79
كَانُوا۟ لَا يَتَنَاهَوْنَ عَن مُّنكَرٍ فَعَلُوهُ ۚ لَبِئْسَ مَا كَانُوا۟ يَفْعَلُونَ
kānū lā yatanāhawna ʿan munkarin faʿalūhu labi'sa mā kānū yafʿalūna
they did not forbid each other to do wrong. How vile their deeds were!
They used not to forbid one another from Al-Munkar (wrong, evil-doing, sins, polytheism, disbelief) which they committed. Vile indeed was what they used to do.