Question 1683) - You mentioned in the previous chapter that if the husband denies the child to whom his wife gave birth to, then Li'an becomes compulsory upon him. We wish to know what is Li'an and how is it conducted?

A: If a man accuses [Qazaf] his wife of Zina, and both of them are legally qualified to testify, and the woman is such whose slanderer will be inflicted with the penal punishment [Hadd]; or he denies the lineage of her child; and the woman demands her rights when slandered; then he will have to undergo Li'an. If he refuses to then the judge will detain him until he either, commences the Li'an or he belies his statement in which case the punishment of slander will be inflicted upon him.
The procedure of Li'an is that the husband presents himself before the judge and will take an oath four times. In each he will say, "I testify by Allaah that I am certainly of the true ones when I accuse this woman of adultery." At the fifth time he will state that may the Allaah's curse definitely be upon him if he is of the liars in accusing her of adultery. He should indicate to her in all this. The woman will then testify four times, saying in each Arsh (testification), "I testify by Allaah that he is certainly of the liars in accusing me of adultery." The fifth time she will say that may Allaah's anger be upon her if he is of the true ones in accusing her of adultery.

~ al-Quduri~