Enjoin what is good and forbid what is wrong is an often quoted phrase, used in the Qur'an. This expression is the base of the Islamic institution of hisbah and sometimes referred to by this word. Hisbah forms a central part of Islamic doctrine, and is explicitly referred to in the two of the Shi'aBranches of Religion, Commanding what is Just and Forbidding what is Evil.
This is one of the large differences between Islam and most other religions. In Christianity, for example, one is responsible for one's own sins and virtues. In Islam, one is responsible to force others not to sin, and to force them "to do good" (as defined by the Qur'an).
The verses below here are by no means an exhaustive list, it is repeated many times more.
Ye are the best of peoples, evolved for mankind, enjoining what is right, forbidding what is wrong, and believing in Allah. If only the People of the Book had faith, it were best for them: among them are some who have faith, but most of them are perverted transgressors.
Let there be people among you, who invite to the best [in religion]; and command that which is just, and forbid that which is evil; and they shall be happy.
"Those who follow the apostle, the unlettered Prophet, whom they find mentioned in their own (scriptures), - in the law and the Gospel; - for he commands them what is just and forbids them what is evil; he allows them as lawful what is good (and pure) and prohibits them from what is bad (and impure); He releases them from their heavy burdens and from the yokes that are upon them. So it is those who believe in him, honour him, help him, and follow the light which is sent down with him, - it is they who will prosper."
And the faithful men, and the faithful women are friends one to another: They command that which is just, and they forbid that which is evil; and they are constant at prayer, and pay their appointed alms; and they obey God, and his apostle: Unto these will God be merciful; for he [is] mighty [and] wise.
