The obligation of li'an (mutual oath-swearing in an accusation of adultery) when a man finds his wife with another man

Question:
He says: Honorable Shaykh, may Allah grant you success. If a man finds another man with his wife, is mutual oath-swearing obligatory for the husband? And does he commit a sin if he leaves it?

Answer:
If he accuses her of adultery, then mutual oath-swearing is obligatory, or the hadd punishment for false accusation is carried out against him. As for the mere presence of a non-mahram man with her, this does not indicate what indicates adultery; this indicates seclusion. He is subjected to discretionary punishment for this, and she is also subjected to discretionary punishment. As for the hadd punishment for false accusation or mutual oath-swearing, it does not apply based on mere seclusion. This is an accusation, this is merely an accusation. Yes.