There are many Hadith related with regard to the issue of enjoining good and forbidding evil. For instance, the Prophet (peace be upon him) said that Allah (Glorified and Exalted be He)
says: "Enjoin good and forbid evil before you supplicate to Me but I will not answer you, and before you ask Me but I will not give you, and before you turn to Me for help but I will not help you."
In another narration reported on the authority of Hudhayfah, the Prophet (peace be upon him) said: "By Him in Whose Hand is my soul! You will enjoin righteousness and forbid evil, or else Allah is about to send a punishment
Then, you will supplicate to Him, but He will not answer your supplication." (Related by Imam Ahmad)
The task of enjoining good and forbidding evil is pivotal, as stated above. In a Hadith narrated on the authority of Ibn Mas'ud by Ahmad, Abu Dawud and AlTirmithy,the Prophet (peace be upon him) said: "When the Children of Israel fell into sins, their religious scholars forbade them, yet they did not desist; then they (i.e., the scholars) sat with them in their assemblies, ate with them and drank with them, so Allah caused the hearts of some to be tainted by the others and cursed them: 'by the tongue of Dawud (David) and ' Isa (Jesus), son of Maryam (Mary). That was because they disobeyed and used to transgress the bounds (in their disobedience to Allâh, i.e. commit crimes and sins). In another narration, it reads: "The first failing to begin among the Children of Israel was that a man would meet another man and say, 'O so and so! Fear Allah and abstain from what you are doing. It is not lawful for you.' Then he would meet him again the next day but this (the sin he saw him doing) would not prevent him from eating, drinking and sitting with him. When they did this, Allah caused the hearts of some to be tainted by the others."
Therefore, we should beware lest we suffer a fate similar to that of those people, particularly there are some Hadiths stating that neglect of the obligation of enjoining good and forbidding evil prevents answering supplications and achieving victory. Indeed, it is a great catastrophe. Part of the punishment for neglecting this obligation includes the defeat and disunity of the Muslims, their enemies' control over them and unacceptance of their supplications Allah forbid.
Enjoining good and forbidding evil may become an individual obligation on the Muslim who sees an evil and there is nobody else to remove it. In this case, they must remove the evil on condition that they are able to. The Prophet (peace be upon him) said: "Anyone of you who sees something evil, let them rectify it with their hand (by taking action); if they cannot, then with their tongue (by speaking out);
and if they cannot, then with their heart (by hating it and feeling that it is wrong); and that is the weakest of Iman (faith)." (Related by Muslim in his Sahih [Authentic Hadith Book])