Gemara

R. Aba: "Asher Lo cha'Das" - until now, Esther was forced to be with Achashverosh. This time, she would go willingly.

"V'Cha'asher Ovadti Ovadti" - just like I was lost from my father's house (orphaned), I am lost to you (as a wife, for now I go willingly).

Sanhedrin 74a - R. Yochanan: Chachamim voted and concluded that if a person is told to transgress or else be killed, he may (Tosfos; Rambam - must) transgress, with three exceptions (for which he must forfeit his life): idolatry, Arayos, and murder.

(Beraisa - Rebbi) Question: "Ki Ka'asher...u'Retzacho Nefesh" connotes that we learn the law of Na'arah Me'orasah from that of a murderer. But it says explicitly that we do not kill her because she was forced!

Answer: Really, Na'arah Me'orasah teaches about murder. The two are equated. Just like one may kill one who seeks to rape a Na'arah Me'orasah, one can kill a pursuer (who seeks to kill someone).

Also, just like one must forfeit his life and not murder, one must forfeit his life and not transgress Arayos.

Reasoning requires one to forfeit his life and not murder. One does not know if he is more worthy to live than the one whom he is told to kill!

Question: Esther was married to Achashverosh in public (i.e. many Yisraelim knew about it. She should have refused and forfeited her life!)

Answer #1 (Abaye): She was Karka Olam (passive, until she went to the king on Mordechai's command. Mesiras Nefesh is required only when one is told to do an action.)

Answer #2 (Rava): If a Nochri wants a Yisrael to transgress for the Nochri's benefit, even in public he need not forfeit his life.

Support (Rava, for himself): On their idolatrous festivals, Nochrim demand that we give them Kelim with coals (for their rituals). Even though this pertains to idolatry, we cooperate. We do not forfeit our lives!

We must say that since they intend for their own pleasure, it is permitted.

75a: A case occurred, a man became sick from desire for a certain woman. Doctors said that he will recover only if he has relations with her. Rabanan said that it is forbidden, even if he will die. The doctors suggested that perhaps it will help if she stands naked in front of him, or talks with him in back of the fence. Each time Rabanan forbade, even though this will cause his death.

R. Yakov bar Idi and R. Shmuel bar Nachmani argued about whether she was married or single.

Question: If she was married, we understand why Rabanan were so stringent. But if she was single, why were they so stringent?

Answer #1 (Rav Papa): It would have been embarrassing to her family.

Answer #2 (Rav Acha brei d'Rav Ika): They were concerned lest Benos Yisrael be indecent (stand in front of men and be given to men for relations).

Kidushin 40a: A woman tempted R. Tzadok to sin. He requested something to eat first. While she was heating the oven, R. Tzadok entered it. He explained that this is (a taste of) his future punishment (burning in Gehinom) for sinning. She left him alone.

Rav Kahana was selling women's baskets. A woman asked him to sin; he said that he needed time to adorn himself. He went to the roof and jumped off; Eliyahu caught him.

Yevamos 53b (Rava): A man is never considered forced regarding Arayos, since Kishuy (an erection) comes only willfully!

Rishonim

The Rif and Rosh (Sanhedrin 17a and 8:3) bring the ruling of R. Yochanan.

Rambam (Hilchos Yesodei ha'Torah 5:1,2): All of Yisrael are commanded about Kidush Hash-m. Regarding idolatry, Arayos and murder, if one is told to transgress or be killed he must submit to be killed.

Kesef Mishneh: The Rambam rules like Rava. He holds like the Ramban, who says that relations with a Nochri is not considered Arayos. If it were, it would be forbidden even if the Nochri intends for his own benefit.

Ba'al ha'Ma'or (Sanhedrin 17b DH Abaye): One may not benefit from any of the three Aveiros even for Piku'ach Nefesh, e.g. to talk with a girl in back of the fence. Only opinion that she was single calls this a decree (to inhibit Pritzus of Benos Yisrael. If she was married, it was Arayos and mid'Oraisa it was forbidden.)

Question: Esther was "l'Vas" (a wife) to Mordechai. Why did the Gemara ask only why she was not Moser Nefesh for Kidush Hash-m? Also, she should have been Moser Nefesh for Arayos!

Answer #1 (Rosh, ibid.): Esther did not do an action. The Gemara knew that passivity exempts from Mesiras Nefesh for Arayos. It thought that this does not exempt from Mesiras Nefesh to avoid Chilul Hash-m.

Answer #2 (Ba'al ha'Ma'or, ibid.): Mesiras Nefesh is never required when the Nochri intends for his own benefit. We learn from Esther. This was in public and it was Arayos. The Gemara preferred to ask why Esther was not Moser Nefesh for Kidush Hash-m, as opposed to for Arayos, for it is not clear that she was married to Mordechai. Even if she was married, the Chiyuv Misah for Eshes Ish applies only to "Eshes Re'ehu", not to a Nochri. Abaye and Rava do not argue with each other; both of their answers are true. Even if they argue, the Halachah follows Rava, who permits when the Nochri intends for his own benefit. One must be Moser Nefesh for Na'arah Me'orasah only when others force him to transgress, but not if she herself forces him for her own desire. The Yerushalmi and the She'altos support this.

Rebuttal (Milchamos Hash-m): R. Tzadok and Rav Kahana were ready to kill themselves rather than sin with Nochriyos who intended for their own benefit (Kidushin 40a). Surely they would not go beyond the letter of the law to kill themselves! "V'Ach Es Dimchem l'Nafshoseichem Edrosh" forbids suicide. The Yerushalmi forbids Mesiras Nefesh beyond the letter of the law.

Note: The Shach (YD 157:1), citing SMaK, says that people who killed themselves because they feared that they would be unable to resist temptation to sin are Kedoshim Gemurim. We learn from Sha'ul. Orchos Chayim (brought in Bedek ha'Bayis) brings this opinion. He says that others forbid; they hold that Sha'ul did improperly. The Ramban (cited in Beis Yosef YD 345 DH v'Chen) says that Sha'ul killed himself due to Ones.

Milchamos Hash-m (continued): We never find that it is praiseworthy for a sick person to refrain from transgressing to save his life. We find that Chachamim did not allow a man to even speak with a girl for Piku'ach Nefesh, even though it was for his desire.

Suggestion: Perhaps it was forbidden because there was no Ones from her perspective!

Rejection (Milchamos Hash-m): Ha'na'as Atzman permitted Esther even though it was in public. The Gemara did not ask about Arayos because only Na'arah Me'orasah and Eshes Ish are considered Arayos. There is no Misah or Kares for Bi'as Nochri with a Bas Yisrael; it is only a Lav. We cannot learn from Na'arah Me'orasah at all. However, Bi'as Yisrael with a Nochris is Arayos, for Kana'im Pog'im Bo, which is like Misah and Kares ("U'Vo'al Bas Ben Nechar; Yachres Hash-m" - Malachi 2:11). Kana'im Pog'im Bo does not apply to Bi'as Nochri with a Bas Yisrael. Shem's Beis Din decreed against this when it is Zenus. The episode was considered Zenus, for Achashverosh gathered and had relations with all the women. Even though Achashverosh married Esther, forced marriage is not marriage. And even though through marriage it is not Arayos (only a Lav "V'Lo Sischaten Bam"). Only Bi'as Yisrael with a Nochris is Arayos, because it produces an idolater; the child is a Nochri, like her. The opinion that Esther was married to Mordechai must hold like Abaye, who permits because of Karka Olam. Rava must hold that she was not married to Mordechai. Alternatively, even though she was married, Bi'ah with a Nochri is not considered Arayos.

Rambam (ibid. 9): If someone became sick from desire for a certain woman and doctors said that he will live only if he has relations with her, it is forbidden, even if she is single. She may not even talk with him in back of the fence. This is so Benos Yisrael will not be like Hefker, leading to wanton Arayos.

Beis Yosef (YD 157 DH Garsinan): Even though we are lenient regarding a Safek in mortal issues, the Rambam is stringent (like the opinion that she was single) because it is better to be passive. Also, Rav Papa and Rav Acha, who are late Amora'im, explained this opinion, indicating that the Halachah follows it.

Question: Rava implies that if Kishuy came unwillingly, one would be Ones and not need to be Moser Nefesh. But Mesiras Nefesh is required for Arayos!

Answer (Rosh Yevamos 6:1): Mesiras Nefesh is not required when one is Karka Olam, e.g. if one will be thrown on a baby to kill the baby. Also regarding Arayos Karka Olam exempts, e.g. a woman, or a man already in Kishuy (if he does not move). However, a man without Kishuy will surely come to Kihuy if put on Ervah. This is a willful action. Even if the Halachah is Mechayev for Arayos without Kishuy, since he does an act to increase his pleasure he is not considered Ones.

Poskim

Shulchan Aruch (YD 157:1): If a Yisrael is told to transgress Arayos (or idolatry or murder) or be killed, he must be Moser Nefesh. This is even in private when there is no decree, even if the Nochri intends for his own benefit, one must be Moser Nefesh.

Rema: This is only if they want the Yisrael to do an act, e.g. to have relations with a woman. But if they forcibly have relations with a Yisraelis, or if a man was in Kishuy they want to force his Ever onto an Ervah, Nisuch ha'Mayim is not required. It is required for any transgression pertaining to Arayos, even a Lav (without Misah), but not for "V'Lifnei Iver Lo Siten Michshol". Bi'as Nochri with a Bas Yisrael is not considered Arayos.

Shach (10-13): Even though the Rambam holds that one is lashed for Kirvah to Ervah (e.g. hugging) only regarding Chayavei Kerisos, he agrees that Mesiras Nefesh is required even for Arayos mid'Rabanan. Most Poskim hold that Bi'as Yisrael with a Nochris is Arayos only because Kana'im Pog'im Bo, which is only in public. However, the Nimukei Yosef says that it is Chayavei Kerisos and requires Mesiras Nefesh even in private. R. Tam says that Bi'as Nochri with a Bas Yisrael is never Arayos. However, all the Poskim say that if she is an Eshes Ish it is Arayos.