If they are a group of people, it becomes a collective obligation on them in the locality or village or the tribe they live in. If one of them rectify the evil, it will be enough and that person will be rewarded; but if all of them leave this duty, they will all incur sin as is the case with the rest of the collective obligations. Supposing that there is only one scholar living in a particular country or tribe, it becomes an individual obligation on him to teach people, call them to Allah, enjoin them to do good and forbid them from doing evil as much as he can, as stated in the Hadiths mentioned above and supported by Allah's saying: So keep your duty to Allâh and fear Him as much as you can
Scholars, callers to Allah and those who enjoin good and forbid evil, whom Allah guided to be patient, and be hopeful for Allah's reward and be sincere to Him are the people of success and guidance through whom Allah benefits His slaves. Allah (may He be Praised) says: And whosoever fears Allâh and keeps his duty to Him, He will make a way for him to get out (from every difficulty). And He will provide him from (sources) he never could imagine. Allah (Exalted be He) also says: and whosoever fears Allâh and keeps his duty to Him, He will make his matter easy for him. He (Glorified and Exalted be He) says: O you who believe! If you help (in the cause of) Allâh, He will help you, and make your foothold firm. Allah (Exalted be He) says: By Al'Asr (the time). Verily,
Except those who believe (in Islâmic Monotheism) and do righteous good deeds, and recommend one another to the truth [i.e. order one another to perform all kinds of good deeds (AlMa'ruf) which Allâh has ordained, and abstain from all kinds of sins and evil deeds (AlMunkar which Allâh has forbidden], and recommend one another to patience (for the sufferings, harms, and injuries which one may encounter in Allâh's Cause during preaching His religion of Islâmic Monotheism or Jihâd).
Therefore, the successful people in the worldly life and the Hereafter are those who have faith, do righteous deeds,
enjoin one another to truth and enjoin one another to patience.