This is another article in the chapter Justice from the classical manual on Sharia called Reliance of the Traveller. The articles are posted one by one in the order they are given in the book.
O13.0 THE PENALTY FOR ACCUSING A PERSON OF ADULTERY WITHOUT PROOF
013.1 When a person (who has reached puberty and is sane) voluntarily:
(a) accuses another person of adultery or sodomy, whether the accusation is in plain words or allusive words intended as an accusation;
(b) and the accused is someone who could be chaste (def: 013.2) and is not the offspring of the accuser;
then the accuser is subject to the penalty for accusing a person of adultery without four witnesses (A: which, if it concerns his spouse, he may obviate by public imprecation (dis: nl1.1)), no matter whether he is a Muslim, non-Muslim subject of the Islamic state, someone who has left Islam, or is of a group that has a truce with Muslims.
013.2 Someone who could be chaste in this context means someone who has reached puberty, is sane, free, Muslim, and has not committed an act of fornication (0: that is punishable) (A: meaning it has not been legally established (def: r,11.2(0:)).
013.3 . The penalty for making such an accusation without witnesses is to be scourged (def: 012.5) eighty lashes.
013.4 Accusations in plain words include such expressions as “You have committed fornication,” and the like, while allusive words means such expressions as “You lecher,” or “You wretch.” If the latter terms are accompanied by the intention to accuse, they amount to an accusation, though if not, they do not. The accuser is the one whose word is accepted (A: when there is no proof, if he swears an oath) as to what he intended by such allusive words.
013.5 If someone accuses a whole group of people of adultery who could not possibly all be guilty, such as saying, “All the people in Egypt are adulterers,” he is disciplined (def: 017). But when his accusation is not impossible, such as saying, “The So-and-so clan are adulterers,” then he must bear a separate penalty for every single person in the group.
013.6 Someone who twice accuses someone of adultery without witnesses is punished only once. Someone who accuses a person of adultery and is punished for the accusation. but then again accuses the person of the same act of fornication is merely disciplined (def: 017).
013.7 When someone accuses a person who could possibly be chaste (def: 013.2) of adultery, but the accuser has not yet been punished at the time the accused subsequently commits an act of fornication, then the accuser is not punished.
013.8 The penalty for accusing a person of adultery without witnesses is only carried out when the Islamic magistrate is present, and the accused requests that it be carried out. If the accused forgives the offender, there is no punishment.
013.9 When an accusation has been made, if the accused dies (A: before the accuser has been punished), then his right (A: to demand that the punishment be carried out) is given to his heirs.