Surah 49. Al-Hujurat, Ayah 12

I.e., guesswork that may lead to unfounded suspicion of another person's motives: see note [22] on 24:19 .

 Backbiting people is likened to eating their dead bodies. So if eating someone’s flesh is detestable, then backbiting them is no different.

Most kinds of suspicion are baseless and to be avoided, and some are crimes in themselves: for they do cruel injustice to innocent men and women. Spying, or enquiring too curiously into other people's affairs, means either idle curiosity, and is therefore futile, or suspicion carried a stage further, which almost amounts to sin. Back-biting also is a brood of the same genus. It may be either futile but all the same mischievous, or it may be poisoned with malice, in which case it is a sin added to sin.

No one would like even to think of such an abomination as eating the flesh of his brother. But when the brother is dead, and the flesh is carrion, abomination is added to abomination. In the same way we are asked to refrain from hurting people's feelings when they are present; how much worse is it when we say things, true or false, when they are absent!