During the night of Isra’ I passed by a group of people scratching their faces with their fingernails so I said “O Jibril, who are they?” Jibril said “they are people who backbite and humiliate others.”
Imam Ghazali (rh) said:
“Backbiting is more evil than 30 fornications in Islam, such is reported in hadith of the Prophet (saw)”
Backbiting is defined as talking about a third person, which if heard, that person he will not like it. The subject could be about his physical flaw, his words, his actions, his religion, his life, his house, his clothes, his animal, his ethnicity or anything else. These are all deemed backbiting and cruel (zolim), even if the accusations are all true.
Know that talking behind somebody’s back is sometimes allowed in 6 circumstances because these could bring good outcomes:
1. In reporting acts of injustice to the authority (qadhi); or report acts of injustice by an authority to the ruler (sultan).
2. In reporting sinful behavior with the intent that the perpretor cease doing it.
3. In talking about others in order to get a ruling (fatwa) from a mufti, such as “somebody is being cruel to me, what is your verdict, and what should I do about it?”
4. To prevent a person from befriending a sinner, as in saying “don’t mix with him, he is a sinner, a tyrant, or evil.”
5. To mention a name, which is tied to a deficiency he is well known for such as “the Blind”, “the Leper”, “the Limp”.
6. To mention somebody who is well know for being a sinner such as famous for his cruelty, fornication, drinking, thievery or others.