Forbidding what is evil (Arabic: النهي عن المنكر Nahy ani l-Munkar), is a part of Islam and means, for example, to oppose injustice. In a more political and social context, Muslims are divided: Some believe that one should not take a social stance unless the Caliph orders.
Etymology
It is derived from the Quranic command what is good and forbid what is wrong.
The phrase "Forbidding what is Evil" comes from several Qur'anic ayah (verses). "al-Munkar" means literally "the rejected".
See also: Ma'ruf
References
Forbidding what is evil Wikipedia(Text) CC BY-SA