The Muslim has to guard his tongue and avoid things that have been forbidden. Among these forbidden things which people often take lightly are gheebah (backbiting), buhtan (slander) and nameemah (malicious gossip).
Buhtan or slander means saying things about a Muslim that are not true, or in other words telling lies about him.
For example: Describing as a kaafir one who has been described as such by Allaah or by His Messenger (saw) is obligatory but it is not permissible to follow one’s own whims and desires & accuse someone without bringing proof.
The slander for which the hadd punishment must be carried out on the slanderer is accusation of zina (fornication or adultery) or homosexuality. In that case the slanderer must be given eighty lashes, if he does not produce four witnesses to testify to the truth of what he is saying, because Allaah says (interpretation of the meaning):
Words which may be used in slanderous ways are of two types: explicit or implicit.
Explicit words are those which cannot be understood in any other way than as an accusation of zina or homosexuality, and the slanderer’s claims that he meant something other than slander cannot be accepted. Examples include saying “O adulterer”, “You committed zina” or “O homosexual”.
As for implicit phrases, these are words that may be taken as slander or they may be understood otherwise. In this case the slanderer is to asked what he meant, and he has to tell the truth, because carrying out the hadd punishment on him in this world is easier to bear than punishment in the Hereafter.