Enjoinment of good and disavowal of evil could be an individual obligation for the one who witnesses the evil, if no one else disavows it and if he is capable of doing so. In such a case, he is obliged to disavow it according to many proofs, the most direct of which is the Prophet's (peace be upon him) saying, "Whoever, among you, sees something abominable should rectify it with his hand; and if he has not enough strength to do it, then he should do it with his tongue; and if he has not enough strength to do it, (even) then he should (abhor it) from his heart, and that is the least of Faith." Related by Muslim in his
Rejecting of evil acts by the heart is obligatory on every Muslim since it is possible for all, through renunciation of abomination, abhorrence of it and separation from its people upon inability to rectify it with the hand or the tongue.
For Allah (Exalted be He) says, And when you (Muhammad ﺻﻠﻰ ﺍﷲ ﻋﻠﻴﻪ ﻭﺳﻠﻢ) see those who engage in a false conversation about Our Verses (of the Qur'ân) by mocking at them, stay away from them till they turn to another topic. And if Shaitân (Satan) causes you to forget, then after the remembrance sit not you in the company of those people who are the Zâlimûn (polytheists and wrongdoers).
He (Exalted be He) also says inSurah AlNisa', And it has already been revealed to you in the Book (this Qur'ân) that when you hear the Verses of Allâh being denied and mocked at, then sit not with them, until they engage in a talk other than that; (but if you stayed with them) certainly in that case you would be like them.
Allah (Exalted be He) also says: And those who do not bear witness to falsehood, and if they pass by some evil play or evil talk, they pass by it with dignity. The meaning of "do not bear witness to falsehood" implies not attending it.