Gemara

(Beraisa): If a Yisrael raped a woman and divorced her, he remarries her, and he is not lashed, even though the Aseh pgrecedes the Lav!

The Torah did not have to say "v'Lo Sihyeh l'Ishah" regarding Motzi Shem Ra, for he is already married to her. We use it to teach that if Motzi Shem Ra divorces her he is not lashed (rather, he remarries her). We learn a rapist from Motzi Shem Ra.

15b (A Tana (reciter of Beraisos)): If a Lav is Nitak l'Aseh, (the Aseh fixes the Lav;) if one transgressed and) fulfilled the Aseh; he is not lashed. If he was Mevatel the Aseh, he is lashed.

Rejection (R. Yochanan): Either lashes depend on whether or not he fulfilled the Aseh, or whether or not he was Mevatel it! The latter is correct.'

(Reish Lakish): It depends on whether or not he fulfilled it.

16a - Question: According to the opinion that lashes are for Bitul of the Aseh, how can a rapist be Mevatel the Mitzvah to remarry her?

Answer: He was Madir her (forbade her through a vow) Al Da'as Rabim (according to the will of many people). It cannot be permitted.

Kesuvos 39a (Mishnah): A rapist must marry her even if she is lame, blind or leprous. If he found immorality in her, or if she is Asur to a Yisrael, he may not stay married to her. "She will be his wife" - she must be proper for him.

39b (Beraisa): She or her father can block the marriage.

(Beraisa): Even though a rapist pays a fine immediately, when he divorces her she has no claim against him.

This means that when she decides to leave him, she has no claim.

(Continuation of Beraisa): If he dies, the fine he had paid is in place of a Kesuvah;

R. Yosi bar Yehudah says, she has a Kesuvah of 100;

The first Tana holds that we enacted Kesuvah lest it be light in his eyes to divorce her. A rapist cannot divorce her, so no Kesuvah was enacted. R. Yosi bar Yehudah is concerned lest he pain her until she will want to leave him.

40a - Question (Rav Kahana): When she is forbidden to Yisraelim, the Mitzvas Aseh to marry her should override the Lav!

Answer (Rav Zvid of Nehardai): An Aseh overrides a Lav only when there is no other way to fulfill the Aseh. Here, if she says that she does not want to marry him, there is no longer an Aseh!

Rishonim

Rif and Rosh (3b and 3:1): R. Yochanan told the Tana to teach that lashes depend on whether or not he fulfilled the Aseh.

Rif and Rosh (Kesuvos 14a and 3:6): She or her father can block the marriage. When she leaves him, she has no claim against him.

Rambam (Hilchos Na'arah 1:5): If she was forbidden to him, even due to an Isur Aseh or Sheniyos (mid'Rabanan), he may not marry her. Similarly, if he found immorality in her after marrying her, he must divorce her. "She will be his wife" refers to someone proper for him

Kesef Mishneh: Why does the Rambam forbid to marry a Sheniyah? Mid'Oraisa, she is proper for him! Perhaps "you will guard My guarding" is a source for Chachamim to forbid Sheniyos, so she is not called 'proper for him.' In any case we can say so, for it says "Lo Sasur."

Rambam (7): Even though a rapist is warned "Lo Yuchal Leshalchah Kol Yamav", since this is preceded by an Aseh "v'Lo Sihyeh l'Ishah", this is a Lav ha'Nitak l'Aseh, and one is not lashed for it unless he did not fulfill the Aseh. Therefore, if he transgressed and divorced her, we force him to remarry her, and he is not lashed. If she died before he remarried her, or she became Mekudeshes to someone else, or he is a Kohen who may not marry a divorcee, he is lashed, for he transgressed a Lav and cannot fulfill its Aseh.

Poskim

Shulchan Aruch (EH 177:3): If one raped a virgin, he must marry her, on condition that she and her father want, even if she is lame or blind. He must divorce her only with her consent, therefore, he need not write a Kesuvah for her. If he transgressed and divorced her, we force him to remarry her.

Beis Yosef (DH v'Ha): According to Rashi, R. Yochanan holds that one is lashed only if he was Mevatel the Aseh, i.e. he made it impossible to fulfill by forbidding her through a vow that cannot be annulled. The Halachah follows R. Yochanan, so he is not lashed if he divorced her and she died or became Mekudeshes to another man. The Rambam says that he is lashed. He had the Rif's text, in which R. Yochanan holds that one is lashed if he was warned 'you must fulfill the Aseh' and he did not do so Toch Kedei Dibur.

Radvaz (1:68, cited in Pischei Teshuvah 7): If after he raped her he forbade himself to benefit from her, it does not exempt him from her. The Mishnah says that he is forced to marry her! If anyone can exempt himself from her, the Aseh "Lo Sihyeh l'Ishah" was written in vain! When the Torah forbids her, this precedes the Aseh to marry her, so the Aseh does not override. The Lav not to divorce her does not strengthen the Aseh to marry her, for they do not apply at the same time. Even if she is a Sheniyah, Chachamim have the power to override Torah by telling someone to be passive. Vows take effect on Mitzvos between man and Hash-m (Matzah, Sukah...), but not on Mitzvos between man and man. A borrower may not forbid all his property to the lender! The same applies here. The vow does not take effect to uproot her rights (that he must marry her). We force him to appease her, so she will say that she does not want him. He must offer her a standard amount for girls of the city to say so. If she is not appeased, he need not offer her a fortune. This is Ohnes. He is exempt form his vow, and he marries her and he can never divorce her.

Note: The Gemara says that if he was Madir her, he was Mevatel the Mitzvah and he is lashed! The Radvaz must explain that she vowed and he was Mekayem her vow (Kesuvos 71a calls also this Madir), but if he vowed, it does not forbid her. This is unlike Tosfos (16a DH Kegon).

Pischei Teshuvah (5, citing Radvaz 1:19): If he admitted that he raped her, he exempts himself from the fine, but not from the Mitzvah to marry her, for this is a separate Mitzvah. This is like paying for pain and embarrassment. His admission does not exempt from these. The Rishonim did not explicitly say so because it is obvious.

Pischei Teshuvah (5): Similarly, admission does not exempt from the Isur to remarry her. Likewise, if he divorced her we force him to remarry her, even if there are no witnesses (that he had raped her). One is believed about (obligating) himself more than 100 witnesses. Perhaps he need not write a Kesuvah, since he cannot divorce her (against her will). However, the Gemara says that the fine is in place of a Kesuvah, so since he does not pay a fine, he must write for her a Kesuvah of 100. The Rambam and Shulchan Aruch connote that the primary reason is because he cannot divorce her. This requires investigation.

Maharam MIntz (109): We learn from Kesuvos that if one raped a woman and married her, she is like a non-virgin, and her Kesuvah is only 100.

Pischei Teshuvah (6): The Halachah follows Chachamim, that she has no Kesuvah! Maharam Mintz learns from R. Yosi b'Rebbi Yehudah that she is considered a non-virgin. Chachamim agree, just they exempt from Kesuvah because he cannot divorce her. This is relevant to one who raped a Bogeres. If he chooses to marry her, her Kesuvah is 100.

Shulchan Aruch (4): If she was forbidden to him, even an Isur mid'Rabanan, he may not marry her. Similarly, if he married her and found immorality in her, he divorces her.

Beis Shmuel (4, citing Prishah 12): This is only actual Zenus.

Beis Shmuel (5): The Rambam and Shulchan Aruch connote that he must divorce her. The Tur connotes that it is optional.

Bach (DH Ela): The Gemara says 'he may not keep her'! The Tur understands that it is a Mitzvah to divorce her, but Beis Din does not force him. The Tur says similarly about Overes Al Das.

Pischei Teshuvah (7): Semak (Aseh 182) says that if he has a wife, and there is a Cherem not to marry a second wife, we excommunicate him until he gives her a proper dowry to enable her to marry someone proper for her. I do not know why the Poskim omitted this.

Ya'avetz (Kesuvos 39a): If she wants to leave, we force him to divorce her.

Rema: If he raped her, and afterwards enticed her, this is called rape, even if she later consented.