Li‘aan is Only Valid in the Presence of the Judge or His Representative
16-11-2020 | IslamWeb
Question:
2: if husband and wife do lian in house without anyone's knowledge and without witness can it make them permanently forbidden to each other, please give answer according to 4madhab in islam. But they want to remain married each other, but did it for ignorance
Answer:
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.
Li‘aan is only valid when conducted in the presence of the ruler (judge), as stated by the jurists. If the spouses conducted Li‘aan in the absence of the judge or whoever is acting on his behalf, the (legal) implications of Li‘aan, such as separation of the spouses and other implications, do not take effect.
Al-Qudoori 
from the Hanafi school of jurisprudence, said in At-Tajreed: “Li‘aan must be conducted in the presence of the judge…” [End of quote]
The Maaliki scholar ‘Ulaysh, quoting ‘Iyaadh 
said: “For Li‘aan to be compliant with the Sunnah, it must be proclaimed in the presence of the Imam (judge) or whoever is appointed by him to act on his behalf in this regard.” [End of quote] According to Al-Mudawwanah, Ibn Al-Qaasim asked Imam Maalik where the process of Li‘aan should be carried out. He replied: “In the mosque or in the Imam’s (judge’s) council…”
The Shaafi‘i scholar An-Nawawi said in Al-Majmoo’: “Li‘aan is only valid when conducted at the command of the judge or whoever is acting on his behalf, and this is the opinion of Ahmad …” [End of quote]
The Hanbali scholar Ibn Qudaamah said in Al-Mughni: “Issue no. 1: Li‘aan is only valid when conducted in the presence of the judge or whoever is acting on his behalf. And this is the opinion of Ash-Shaafi‘i, because the Prophet, sallallaahu ‘alayhi wa sallam, commanded Hilaal ibn Umayyah to summon his wife and conducted Li‘aan between them, and also because Li‘aan requires making an oath or giving a testimony, and one of the conditions for the validity of them both (the oath and testimony) is the presence of the judge. If the spouses agree to have Li‘aan conducted between them by someone other than the judge, Li‘aan is invalid because it is fundamentally based on strictness and confirmation of punishment. Therefore, it is valid only when conducted by the judge, just like the Hadd (Corporal punishments prescribed for certain crimes set by the Sharee‘ah).” [End of quote]
Allah Knows best