What is the ruling on marrying an adulterous man who confessed his mistakes and repented from them before she knew him, and does "the adulterer for the adulteress" apply to them? And what is the ruling if the husband cheated and committed adultery after marriage?

Adultery is one of the gravest sins, but Allah accepts the sincere repentance of the adulterer. Repentance involves abandoning the sin, regretting it, and resolving not to return to it, while also concealing one's own sin. If the adulterer repents with a sincere repentance, the description of adultery is removed from him, and it is permissible for a woman to marry him, for the Prophet, peace and blessings be upon him, said: "The one who repents from a sin is like one who has no sin." As for the unrepentant adulterer, he is not a suitable match for a chaste woman. And if a husband commits adultery, the marriage is not dissolved. The interpretation of the verse: "The adulterer does not marry except an adulteress or a polytheist" is a prohibition against a chaste person marrying an adulterer/adulteress, or that "marriage" (نكاح) here means sexual intercourse. Whoever falls into sin must conceal it and not inform anyone.