What should a man do who discovered after his marriage that his 19-year-old wife was not a virgin, and she confessed to him about her previous relationships before marriage, taking into account that he does not want to tarnish the reputation of her parents, who are good people, and that she threatens him with suicide if he tells anyone?

You erred in asking the girl about her committing a grave sin, and she erred by disclosing it. It was her duty to conceal her own sin. Disclosing a sin is tantamount to publicizing it, and Allah does not like the publicizing of evil or the spreading of indecency. Every member of the Ummah of Muhammad is forgiven except those who publicize their sins. Furthermore, the loss of virginity may occur without intercourse, and it is not permissible for you to expose her or to disclose what she told you. Our advice to you is to consider her current state: if she repents and becomes righteous, then keep her and treat her well, strive to raise her in faith, and be a good role model for her. We also warn against the danger of suicide, as it increases misery in the Hereafter.