Allah T'ala says in the Holy Quran:
O you who have believed, avoid much suspicion, for some suspicions are sins. Do not spy, nor should any one backbite the other. Is there any among you who would like to eat the flesh of his dead brother?' Nay, you yourselves abhor it. Fear Allah, for Allah is Acceptor of repentance and All-Merciful. (49:12)
Gheebat (back-biting) has been defined thus: "It is saying on the back of a person something which would hurt him if he came to know of it. " This definition has been reported from the Holy Prophet himself. According to a tradition which Muslim, Abu Da'ud, Tirmidhi, Nasa'i and others have related on the authority of Hadrat Abu Hurairah, the Holy Prophet defined Gheebat as follows:
"It is talking of your brother in a way irksome to him." It was asked: "What, if the defect being talked of is present in my brother ?" The Holy Prophet replied: "If it is present in him, it would be Gheebat; if it is not there, it would be slandering him."
In another tradition which Imam Malik has related in Mu'watta, on the authority of Hadrat Muttalib bin `Abdullah, "A person asked the Holy Prophet: What is Gheebat? The Holy Prophet replied: It is talking of your brother in a way irksome to him. He asked: Even if it is true, O Messenger of Allah? He replied: If what you said was false, it would then be a calumny."
These traditions make it plain that uttering a false accusation against a person in his absence is calumny and describing a real defect in him Gheebat; whether this is done in express words or by reference and allusion, in every case it is forbidden. Likewise, whether this is done in the lifetime of a person, or after his death, it is forbidden in both cases.
According to Abu Da'ud, when Ma`iz bin Malik Aslami had been stoned to death for committing adultery, the Holy Prophet on his way back heard a man saying to his companion: "Look at this man: Allah had concealed his secret, but he did not leave himself alone till he was killed like a dog!" A little further on the way there was the dead body of a donkey lying rotting. The Holy Prophet stopped, called the two men and said: "Come down and eat this dead donkey." They submitted: "Who will eat it, O Messenger of Allah?" The Holy Prophet said: "A little before this you were attacking the honor of your brother: that was much worse than eating this dead donkey."
The only exceptions to this prohibition are the cases in which there may be a genuine need of speaking in of a person on his back, or after his death, and this may not be fulfilled without resort to backbiting, and if it was not resorted to, a greater evil might result than backbiting itself. The Holy Prophet has described this exception as a principle, thus: "The worst excess is to attack the honour of a Muslim unjustly." (Abu Da'ud).
In this saying the condition of "unjustly" points out that doing so "with justice" is permissible. Then, in the practice of the Holy Prophet himself we find some precedents which show what is implied by "justice" and in what conditions and cases backbiting may be lawful to the extent as necessary.
Once a desert Arab came and offered his Prayer under the leadership of the Holy Prophet, and as soon as the Prayer was concluded, walked away saying: "O God, have mercy on me and on Muhammad, and make no one else a partner in this mercy beside the two of us." The Holy Prophet said to the Companions: `What do you say: who is more ignorant: this person or his camel? Didn't you hear what he said?" (Abu Da`ud). The Holy Prophet had to say this in his absence, for he had left soon after the Prayer was over. Since he had uttered a wrong thing in the presence of the Holy Prophet, his remaining quiet at it could cause the misunderstanding that saying such a thing might in some degree be lawful; therefore, it was necessary that he should contradict it.
Two of the Companions, Hadrat Mu`awiyah and Hadrat Abu Jahm, sent the proposal of marriage to a lady, Fatimah bint Qais. She came to the Holy Prophet and asked for his advice. He said: "Mu`awiyah is a poor man and Abu Jahm beats his wives much." (Bukhari, Muslim). In this case, as there was the question of the lady's future and she had consulted the Holy Prophet for his advice, he deemed it necessary to inform her of the two men's weaknesses.
One day when the Holy Prophet was present in the apartment of Hadrat 'A'ishah, a man came and sought permission to see him. The Holy Prophet remarked that he was a very bad man of his tribe. Then he went out and talked to him politely. When he came back into the house, Hadrat `A'ishah asked: "You have talked to him politely, whereas when you went out you said something different about him. " The Holy Prophet said, "On the day of Resurrection the worst abode in the sight of Allah will be of the person whom the people start avoiding because of his abusive language." (Bukhari, Muslim). A study of this incident will show that the Holy Prophet in spite of having a bad opinion about the person talked to him politely because that was the demand of his morals; but he had the apprehension lest the people of his house should consider the person to be his friend when they would see him treating him kindly, and then the person might use this impression to his own advantage later. Therefore, the Holy Prophet warned Hadrat `A'ishah telling her that he was a bad man of his tribe.
Once Hind bint 'Utbah, wife of Hadrat Abu Sufyan, came to the Holy Prophet and said: "Abu Sufyan is a miserly person: he does not provide enough for me and my children's needs. " (Bukhari, Muslim). Although this complaint from the wife in the absence of the husband was backbiting, the Holy Prophet pemitted it, for the oppressed has a right that he or she may take the complaint of injustice to a person who has the power to get it removed.
From these precedents of the Sunnah of the Holy Prophet, the jurists and traditionists have deduced this principle: 'Gheebat (backbiting) is permissible only in case it is needed for a real and genuine (genuine from the Shari'ah point of view) necessity and the necessity may not be satisfied without having resort to it". Then on the basis of the same principle the scholars have declared that Gheebat is permissible in the following cases:
(1) Complaining by an oppressed person against the oppressor before every such person who he thinks can do something to save him from the injustice.
(2) To make mention of the evils of a person (or persons) with the intention of reform before those who can do expected to help remove the evils.
(3) To state the facts of a case before a legal expert for the purpose of seeking a religious or legal ruling regarding an unlawful act committed by a person.
(4) To warn the people of the mischiefs of a person (or persons) so that they may ward off the evil, e g. it is not only permissible but obligatory to mention the weaknesses of the reporters, witnesses and writers, for without it, it is not possible to safeguard the Shariah against the propagation of false reports, the courts against injustices and the common people or the students against errors and misunderstandings. Or, for instance, if a person wants to have the relationship of marriage with somebody, or wishes to rent a house in the neighborhood of somebody, or wants to give something into the custody of somebody, and consults another person, it is obligatory for him to apprise him of all aspects so that he is not deceived because of ignorance.
(5) To raise voice against and criticise the evils of the people who may be spreading sin and immorality and error, or corrupting the people's faith and persecuting them.
(6) To use nicknames for the people who may have become well known by those names, but this should be done for the purpose of their recognition and not with a view to condemn them. (For details, see Fat-h al-Bari, vol. X, p. 362; Sharah Muslim by An-Nawawi; Riyad us-Salihin; al-Jassas, Ahkam al-Qur an; Ruh al-Maani commentary on verse wa a yaghtab ba 'dukum ba 'dan).
Apart from these exceptions it is absolutely forbidden to speak ill of a person behind his back. If what is spoken is true, it is Gheebat; if it is false, it is calumny; and if it is meant to make two persons quarrel, it is slander. The Shari'ah has declared all these as forbidden. In the Islamic society it is incumbent on every Muslim to refute a false charge made against a person in his presence and not to listen to it quietly, and to tell those who are speaking ill of somebody, without a genuine religious need, to fear God and desist from the sin. The Holy Prophet has said: If a person does not support and help a Muslim when he is being disgraced and his honour being attacked, Allah also does not support and help him when he stands in need of His help; and if a person helps and supports a Muslim when his honour is being attacked and he is being disgraced, Allah Almighty also helps him when he wants that AIlah should help him. (Abu Da'ud).
As for the backbiter, as soon as he realizes that he is committing this sin, or has committed it, his first duty is to offer repentance before Allah and restrain himself from this forbidden act. His second duty is that he should compensate for it as far as possible. If he has backbitten a dead person, he should ask Allah's forgiveness for the person as often as he can. If he has backbitten a living person, and what he said was also false, he should refute it before the people before whom he had made the calumny. And if what he said was true, he should never speak ill of him in future, and should ask pardon of the person whom he had backbitten. A section of the scholars has expressed the opinion that pardon should be asked only in case the other person has come to know of it; otherwise one should only offer repentance, for if the person concerned is unaware and the backbiter in order to ask pardon goes and tells him that he had backbitten him, he would certainly feel hurt.
In the verse, Allah by likening backbiting to eating a dead brother's flesh has given the idea of its being an abomination. Eating the dead flesh is by itself abhorrent; and when the flesh is not of an animal, but of a man, and that too of one's own dead brother, abomination would be added to abomination. Then, by presenting the simile in the interrogative tone it has been made all the more impressive, so that every person may ask his own conscience and decide whether he would like to eat the flesh of his dead brother. If he would not, and he abhors it by nature, how he would like that he should attack the honour of his brother-in-faith in his absence, when he cannot defend himself and when he is wholly unaware that he is being disgraced. This shows that the basic reason of forbidding backbiting is not that the person being backbitten is being hurt but speaking ill of a person in his absence is by itself unlawful and forbidden whether he is aware of it, or not, and whether he feels hurt by it or not. Obviously, eating the flesh of a dead man is not forbidden because it hurts the dead man; the dead person is wholly unaware that somebody is eating of his body, but because this act by itself is an abomination. Likewise, if the person who is backbitten also does not come to know of it through any means, he will remain unaware throughout his life that somebody had attacked his honour at a particular time before some particular people and on that account he had stood disgraced in the eyes of those people. Because of this unawareness he will not feel at all hurt by this backbiting, but his honour would in any case be sullied. Therefore, this act in its nature is not any different from eating the flesh of a dead brother.
(Tafheemul Quran)