Description of Li`an
A husband says: I bear witness by Allah I am truthful concerning the accusations of my wife of adultery.
Then he should point at her if she is present, but if not, he should call her by her full name four times then he should say in the fifth time: The curse of Allah is on me if I am laying.
Then the wife says: I bear witness by Allah that he is lying concerning the accusations [four times], then she should say in the fifth: The wrath of Allah shall be on me if he is truthful in his accusations.
If one of them did not complete the five times or she started Li`an before him, or they started Li`an before the coming of the judge or his deputy, Li`an shall be invalid. If a husband replaces the word "I bear witness" by "I swear" or "I make an oath" or replaced the word "Curse" by "expelling" or the word "wrath" by "discontent," it has two views:
It is a Sunnah to start Li`an in the presence of four or more people in a known time and place. A judge may order someone to put his hand or her hand on the mouth of the husband or the wife in the fifth time and says: Fear Allah, for it is the last time after which she shall be divorced, and the torment of the world is easier than the torment of the Hereafter.
Li`an is valid according to three conditions:
1- It should take place between two competent spouses because of Allah's Saying: "And for those who accuse their wives." So, there is no Li`an between a master and his slave girl and there is no prescribed punishment.
As for the condition "competent," the false accusation of incompetent does not entail a prescribed punishment, and Li`an was ordained to cancel the prescribed punishment.
2- To accuse her falsely with vaginal or anal adultery because it is a false accusation that entails the prescribed punishment. There is no difference between a blind and sighted because of the generality of the Ayah.
3- A wife should belie his false accusation and this should last until the end of the Li`an process because Li`an is still effective as long as she belies, but if she certifies him or drops her right or keeps silent without affirming or denying, the child will be his and Li`an is invalid because it is her right to affirm or deny it, so it cannot be valid without her demand. If there is a child whom a husband wants to deny, he may observe Li`an because he needs it as a sole right which cannot be overlooked by her consent.