Book of Oaths
Introduction
The word aymān (with the hamzah pronounced) is the plural of yamīn. In its original linguistic sense yamīn means “hand,” but it came to signify an oath because, when the Arabs concluded a pact, each party would clasp the other’s right hand.

In the sacred law an oath (yamīn) is the confirmation of a statement by invoking something held in reverence, and doing so in the prescribed manner.

Oaths fall into the following categories:
1 – Words that pass the speaker’s lips unintentionally, such as “wallāhi,” “balā wallāh,” or “tallāh.” This is classed as laghw (an unintentional oath).
2 – An oath about a past event that the swearer believes to be true but later discovers is not; this likewise counts as laghw.
3 – An oath knowingly sworn falsely about a past event. This is the perjurious oath (al-yamīn al-ghamūs). None of these three kinds requires an expiation.
4 – An oath taken deliberately concerning a future matter. This is the oath for which expiation (kaffārah) is due, provided the following conditions are met:
(a) the person swearing is legally accountable;
(b) he takes the oath of his own free choice;
(c) he intends the oath—an utterance that slips out inadvertently does not establish a binding oath.