All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If a man accuses his wife of committing Zina (fornication) before their marriage, Li‘aan is not applicable. Ibn Qudaamah said in Al-Mughni: "If he accuses her of committing Zina after their marriage and attributes the incident to a time before the marriage, he would be liable for the Hadd (prescribed corporal punishment), and Li‘aan is not applicable, regardless of whether she gave birth to a child or not. This is the opinion of Maalik and Abu Thawr. This was also narrated on the authority of Sa‘eed ibn Al-Musayyib and Ash-Sha‘bi. On the other hand, Al-Hasan, Zuraraah ibn Abu Awfa, and the Hanafi scholars held that Li‘aan is applicable in this case because he slandered his wife, and therefore, it is included in the general indication of the verse reading (what means): {And those who accuse their wives [of Zina]…} [Quran 24:6] And also because he accused his wife of committing Zina, and this is similar to the situation if he slanders her without attributing the incident to a time before their marriage. Ash-Shareef Abu Ja‘far narrated another opinion on the authority of Ahmad as well, and Ash-Shaafi‘i said: 'If she has not given birth to a child, Li‘aan is not applicable, but if they have a child, there are two opinions in this regard.'" [End of quote]
Li‘aan is only applicable when a man accuses his wife of committing Zina and she denies it, but when a woman slanders her husband, this does not, on its own, warrant Li‘aan. Al-Maawardi said in Al-Ahkaam As-Sultaaniyyah: "If a woman accuses her husband of committing Zina, she would be liable for the Hadd of slander. Li‘aan is not applicable in this case." [End of quote]
It is impermissible for anyone to accuse another person of committing Zina after they have repented of it. Sincere repentance wipes out the sin of Zina and establishes the repentant person’s chastity. Ibn Qudaamah regarding the ruling on marrying a female perpetrator of Zina, said in Al-Mughni: "If she repents, she is no longer considered a perpetrator of Zina because the Prophet, sallallaahu ‘alayhi wa sallam, said: ‘The one who repents from sin is like one who did not sin.'" [End of quote]
Al-Buhooti said: "As far as slander is concerned, a Muhsan refers to a person who is free, Muslim, sound of mind, and apparently free of any Zina conviction, even if they have committed Zina and then repented of it." [End of quote]
Allah Knows best.