Surah Yunus, Ayat 93

Ayat 93. And indeed We settled the Children of Israel in an honorable dwelling place (Sham and Misr), and provided them with good things, and they differed not until the knowledge came to them. Verily, Allah will judge between them on the Day of Resurrection in that in which they used to differ. 

Hazrat Abdullah bin Mas`ud (May Allah bepleased with him) reported: Messenger of Allah  [SAWW](PBUH) said, "When the Children of Israel became sinful, their learned men prohibited them but they would not turn back. Yet, the learned men associated with them and ate and drank with them. So, they were cursed at the tongues of Dawud and `Isa (Jesus), son of Maryam (Mary), because they were disobedient and were given to transgression.'' At this stage Messenger of Allah  [SAWW]((PBUH) who was reclining on a pillow sat up and said, "No, By Him in Whose Hand my soul is, there is no escape for you but you persuade them to act justly.'' [At-Tirmidhi Hadith # 3047 & 3048].  

Lesson : as mentioned above in Surah Yunus Ayat 93. "and they differed not until the knowledge came to them. Verily, Allah will judge between them" This Hadith tells us that the duty of `Ulama' is to check the people from vice and if, in spite of all their efforts people do not abandon them, they should avoid associating with them because it is a matter of religious reverence and vanity. If they do not do it, they will also be cursed like the disobedient lot. May Allah save us from this negligence.