Is the prescribed punishment for zina (unlawful sexual intercourse) mandatory for someone who committed an act that they ignorantly believed, based on a mistaken definition, was not zina necessitating the حد (prescribed punishment)? And what is the authority that enforces it? And is one obliged to surrender oneself to it? And what is the consequence if it is not enforced? And is marriage permissible with the girl with whom the act occurred? And does an accepted Hajj expiate major sins?

"Unlawful mixing is a cause of evil and corruption, and what transpired between you and that woman is a testament to this. The sin is magnified by the commission of such heinous acts by a married man. Therefore, you must hasten to sincere repentance and beware of every path that leads you to fall into these sins again. Prayer and fasting are among the greatest means of preventing one from falling into transgressions. For zina (fornication/adultery) that necessitates the Hadd punishment, the mere insertion of the glans into the woman's private part is sufficient. In Saudi Arabia, the شرعية (Sharia) court is responsible for implementing the Hadd punishments. However, it is sufficient for you to repent to Allah and conceal your sin; you are not required to refer your matter to a judge for the Hadd to be carried out against you. And whoever repents from his sin, Allah accepts his repentance. As for whether Hajj expiates major sins, please refer to Fatwa No. 42406. Regarding your marriage to this woman, it is permissible on condition of repentance and istibra' (ensuring no pregnancy). However, it is difficult to ascertain whether the Christian woman has abandoned zina or not, and therefore, it is advisable to avoid marrying her."