According to the Qur’an, enjoining what is right and forbidding the wrong is the religious duty of every believer. Allah says:
And (as for) the believing men and the believing women, they are guardians of each other; they enjoin what is right and forbid the wrong and keep up prayer and pay the poor-rate, and obey Allah and His Messenger; (as for) these, Allah will show mercy to them; surely Allah is Mighty, Wise. (9:71)
The guardianship in this verse is explained as: enjoining what is right and forbidding the wrong, keeping up prayers, paying the poor rate and obeying Allah and His Messenger.
In another verse the Muslim nation is honored as the best nation raised for the people because of their religious twin duty of enjoining what is right and forbidding the wrong. Allah says:
You are the best of the nations raised up for (the benefit of) men; you enjoin what is right and forbid the wrong and believe in Allah. (3:110)
The Arabic words in both the verses (9:71 and 3:110) translated here as “right” and “wrong” (enjoin what is right and forbid the wrong) are al-ma‘rūf and al-munkar which literally mean ‘‘acknowledged’’ and ‘‘not acknowledged’’ respectively.
Commenting on the verses 3:102-110, Allamah Tabatabai in his tafsir al-Mizan says the ideal society is that which follows the guidance, And hold fast by the cord of Allah all together and be not divided (3:103). It would only be the right and the good which they would recognize and be “acknowledged” by them; and only the wrong and the evil which they would recognize and “not acknowledge”. If this fine point is not kept in mind, then the only possible explanation would be that the right and the wrong were respectively acknowledged and not acknowledged in the eyes of religion — but not in actual practice of the society.
This explanation goes hand in hand with the verse: and whatever the Messenger gives you, take it, and from whatever he forbids you, keep it back (59:7) which shows that what the Messenger gives you would be right (acknowledged) and what he forbids, would be wrong (not acknowledged) in the eyes of religion. Hence, as per verse 9:71, the religious duty of every believer would be to distinguish between the right and wrong in the eyes of religion such that they can fulfill their duty.