The Ruling on Backbiting One Who Abandons Prayer in Order to Warn Against Him

Question:
If I know that some people do not pray and do not remember Allah, but rather commit evil deeds that anger Allah and His Messenger (peace and blessings be upon him) in every respect, is it permissible for me to backbite them so that people know about them, or is it not permissible for me to do so?
Answer:
You must first advise him, ordering him to do what Allah has commanded and disapproving of what he does that Allah has forbidden. If he complies, even little by little, continue advising him as much as you are able. Otherwise, avoid him as much as you can to guard against fitnah (trial, discord or temptation) and to stay away from what is wrong. After that, you may mention his neglect of obligatory duties and his commission of wrongs when there is a reason to do so, with the intention of identifying him and protecting people from his harm. It may even become obligatory for you to do so if someone asks for your advice regarding living near him, partnering with him, or employing him, for example, or if you fear that a person will fall into his trap and be harmed by him. In that case, you must explain his condition to rescue the people of good from his harm and in the hope that he will repent if he realizes that people have turned away from him and avoided him.
You must not take his bad conduct as a source of comfort for yourself and for people, or as entertainment to amuse yourselves with in gatherings. That is spreading evil, and it causes souls to become numb and lose their sensitivity to hearing about wrongs. You must not fabricate wrongs against him that he has not committed, seeking to further tarnish his reputation and vilify him, for that is lying and slander, and the Prophet (peace and blessings be upon him) forbade it.