Responsa על אסתר 4:20

In the aforementioned responsum of Maharik, regarding Maharil’s question about whether woman who willingly committed adultery against her husband without knowing that it is forbidden is considered unwitting (shogeg), he responded: "In my opinion, it appears that she is not considered unwitting in order to be permitted to her husband, since she intended to betray her husband and cheat on him. After all, Scripture does not say “A man whose wife strays, and betrays God,” which would imply that the law applies only when she intends to violate a prohibition, but “and betrays him.”" Later he writes: "It also seems, in my humble opinion, that there is another proof that the matter does not depend on intent to violate a prohibition, for we learn in the first chapter of Megilla (15a): “‘If I am lost, I am lost’ (ka’asher avadeti avadeti; Esther 4:16): just as I lost my father’s house, so too I will lose you. Until now I have been compelled, but now I am willing.” We learn from this that from that time, she became forbidden to Mordechai. Now, it is clear that Esther did nothing prohibited, and there was not even a smidgen of transgression. Rather, she performed a great mitzva, for she saved all of Israel. Clearly that this is the case, for when she came before the king, the divine spirit rested upon her. But even so, she became forbidden to her husband, Mordechai, as a result of that willing act. Now we may reason a fortiori: if in that case, where there was not a smidgen of transgression, and, on the contrary, she did a mitzva, and yet she was still forbidden to her husband Mordechai, then certainly a woman who committed adultery against her husband, even if she does not know that this is prohibited, is forbidden to him because she nevertheless transgressed, and needs atonement, and is liable to bring an offering."

Therefore, it seems to me, in my humble opinion, that if her actions were definitely necessary to save Israel, then there is no greater compulsion than that. However, it seems from his words that Mordechai was uncertain about that, since he said: “If you are silent at this time, relief and deliverance will rise for the Jews from somewhere else… and who knows whether you became royalty for a time like this?” (Esther 4:14) The meaning of his words is that he was confident that God would send deliverance to the Jews, but he was uncertain whether it would come via Esther or from somewhere else. Thus he asks “Who knows” whether you became queen in order to save Israel—as Ibn Ezra explains. Thus, from the perspective of prohibited adultery of a married woman, despite the uncertainty, it was permitted, for we desecrate Shabbat even for the possibility of saving a life. But with regard to the question of whether she remains permitted to her husband, the uncertainty remains, since indeed, it may have been possible to save them another way, so perhaps she committed adultery willingly and unnecessarily. Thus, Esther said “If I am lost, I am lost,” that now she was going willingly, and due to the uncertainty, she would be forbidden to her husband. But when she reached the chamber of idols, and the divine presence left her, she asked, “Why have You forsaken me? Do You judge unwitting acts as though they were done knowingly? Coerced acts as though they were done willingly?” She was not really wondering about this, since the Torah is explicit that God does not judge coerced acts like those done willingly. Rather, she was wondering: “Are You thus, perhaps, telling me that I should not go? That I am not compelled? That You do not want to save Israel through me?” Therefore, when the divine presence returned to her, she knew that this came from God, and that He wished to rescue Israel only through her. And therefore, for this truly righteous woman, it indeed was not considered adultery—which would have made her forbidden to her husband—since she was entirely coerced.