Surah At-Taubah, Ayat 112

Ayat 112. (The believers whose lives Allah has purchased are) those who repent to Allah (from polytheism and hypocrisy, etc.), who worship Him, who praise Him, who fast (or go out in Allah's Cause), who bow down (in prayer), who prostrate themselves (in prayer), who enjoin (people) for Al-Ma'ruf (i.e. Islamic Monotheism and all what Islam has ordained) and forbid (people) from Al-Munkar (i.e. disbelief, polytheism of all kinds and all that Islam has forbidden), and who observe the limits set by Allah (do all that Allah has ordained and abstain from all kinds of sins and evil deeds which Allah has forbidden). And give glad tidings to the believers. 

Hazrat Abu Sa`id Al-Khudri (May Allah be pleased with him) reported: Messenger of Allah  [SAWW](PBUH) said, "Whoever amongst you sees an evil, he must change it with his hand; if he is unable to do so, then with his tongue; and if he is unable to do so, then with his heart; and that is the weakest form of Faith". [Muslim Hadith # 79].

Lesson : as mentioned above in Surah At-Taubah Ayat 112 "who enjoin (people) for Al-Ma'ruf and forbid (people) from Al-Munkar (i.e. disbelief, and all that Islam has forbidden), and who observe the limits set by Allah." This Hadith contains a very important prescription to prevent the Muslim society from all things which are forbidden in Islam. So long as Muslims adhered to it and ceaselessly and fearlessly performed their obligation of enjoining the right and forbidding the wrong, their society was largely safe from many evils and sins. To abandon the practice of enjoining virtue and forbidding vice is likely to incur the displeasure of Allah. This trend is indeed fraught with the danger of rejection of prayers and supplications by Him.