Whosoever of you sees an evil, let him change it
On the authority of Abu Sa`eed al-Khudree (may Allah be pleased with him) who said: "I heard the Messenger of Allah, may the peace and blessings of Allah be upon him, saying, “Whosoever of you sees an evil, let him change it with his hand; and if he is not able to do so, then [let him change it] with his tongue; and if he is not able to do so, then with his heart — and that is the weakest of faith.” [Muslim]
This Hadeeth is considered one of the mainstays of the most important chapters of Fiqh. The Jurists have written a great deal of researches in which they have discussed the issues, and they have made more mention of the disagreement about the ruling on enjoining what is good and forbidding what is evil, how the person can observe that, who is entrusted with performing this task, what are the conditions to be fulfilled, and what are the conditions in which it is permissible to enjoin what is good and forbid what is evil, and when to suffice with rejecting the evil only with the heart ... in addition to the other rulings and etiquettes.
The general view of this Hadeeth shows us that Islam is a religion that has made what is good known as the first of the principles of ethics and ideals. Islam confirmed ordering it and warned against abandoning it if one is able to perform it. Islam considered ordering what is good to be one of the greatest duties for those who are aware of the relevant rulings and are able to perform it.
That which is good is all that Islam ordered or recommended to do. On the opposite is that which evil that encompass everything Islam rejected and warned against.