The Islamic ruling on lian is based on the following four Quranic verses:
Allah (swt) says in the Holy Quran: ‘And for those who accuse their wives but have no witnesses except themselves, let the testimony of one of them be four testimonies (testifies four times) by Allah that he is one of those who speak the truth’. (TMQ-24:6)
‘And the fifth (testimony) (should be) the invoking of the Curse of Allah on him if he be of those who tell a lie (against her)’. (TMQ-24:7)
‘But it shall avert the punishment (of stoning to death) from her, if she bears a witness four times by Allah, that he (her husband) is telling a lie. . (TMQ-24:8)
‘And the fifth testimony should be that the Wrath of Allah be upon her if he (her husband) speaks the truth’. (TMQ-24:9)
‘And had it not been for the Grace of Allah and His Mercy on you (He would have hastened the punishment on you)! And that Allah is the one Who accepts repentance, the All-Wise’. (TMQ-24:10)
The law states that if a man becomes an eye witness to his wife’s illicit sexual relation with her paramour then in such a case, he will require three other witnesses, besides him, to prove his wife’s adultery. Therefore, unless such a man is able to produce three other witnesses in the court, till then his wife’s adultery cannot be proved.
In such cases, it is also quite impossible for the man to tolerate his wife after seeing her with another man in a compromising position. The solution which has been offered by the Shariah for such a man is that he will have to take an oath in a court, before a judge. He will have to take the oath four times that his wife is adulterous and he is being truthful in accusing his wife. If by chance his wife had become pregnant then he may also reject the fatherhood of his wife’s child. In his fifth oath that he takes he will have to say that in case he is lying in the court then may he face the Wrath of Allah (swt).
If his wife also turns around and blames him, i.e. is she also takes an oath (four times) that her husband is lying and then if she says (for the fifth time) that if, in case, her husband is truthful and she is lying then may Allah (swt)’s Wrath be on her so in such a situation she will be left scot-free. In this situation the couple will split.
This law is named Lian because both the husband and the wife agree to the fact that in case they are lying then they deserve to face the Wrath of Allah (swt).
During the lifetime of Prophet Mohammad (saw) many such incidences had taken place and their details are found in the ahadith. It was these incidences against the backdrop of which the verses (24:6-24:10) were revealed.
Verse 24:10 says that if Allah (swt) was not All-Merciful then He would have punished the guilty person immediately. However, since Allah (Swt) is All-Forgiving therefore He conceals the sin of the one who is lying so that if the liar feels guilty later on and repents then Allah (swt) will forgive him. Since Allah (swt) is All-Wise He has provided a proper and easy solution through law of lian for the decent men who have witnessed their wife’s adultery and cannot bear to tolerate her any longer