Gemara

(Beraisa - R. Meir and R. Yehudah): If a woman vowed to be a Nezirah and

her husband heard and did not annul it, it is her fault. He may say that he does not want a wife who vows, so he may divorce her without paying her Kesuvah;

R. Yosi and R. Elazar blame him. If he wants, he can annul. If he does not want a wife who vows, he may divorce her but must pay her Kesuvah.

72a (Mishnah): A woman is divorced without a Kesuvah for transgressing Das Moshe (Torah law). This is feeding to him untithed food, having Bi'ah with him when she is Nidah, not separating Chalah, or vowing and transgressing her vows;

Transgressing vows is grounds to divorce her without a Kesuvah, since children die due to vows of the parents.

(Beraisa - R. Meir): One who knows that his wife vows and transgresses her vows should anger her so she will vow in front of him and he can annul the vows;

Chachamim say, a man cannot live with a snake in a basket (he divorces her without a Kesuvah).

(Beraisa - R. Yehudah): One who knows that his wife does not separate Chalah should separate it himself;

Chachamim say, a man cannot live with a snake in a basket.

R. Yehudah counsels to keep a wife who does not separate Chalah. All the more so, he counsels to keep a wife who transgresses her vows (like R. Meir);

R. Meir counsels to keep a wife who transgresses her vows, but he would counsel divorcing one who doesn't separate Chalah, lest he forget and eat.

101a (Beraisa): When Chachamim said 'she leaves without a Kesuvah', such as one who transgresses Das (Moshe or Yehudis) and accompanying cases, she does not receive Tosefes, all the more so not 100 or 200.

Gitin 90a: If a man does not protest when he sees his wife go out with uncovered hair, weave in public with her elbows exposed, or bathe where men bathe, he is a Rasha. It is a Mitzvah to divorce such a woman.

Rishonim

The Rif and Rosh (32b, and 7:9) bring our Sugya.

Rif: If she was warned, she forfeits her Kesuvah, not only 100 or 200. She does take existing remnants (of her dowry).

Rosh (11:25): Any woman who was permitted when she married, but caused that she must be divorced (e.g. through Zenus), does not receive Ikar Kesuvah or Tosefes. She does take existing remnants of her Nichsei Melug and Tzon Barzel.

Ran (22a DH veli'Chsuvas): Perhaps Overes Al Das loses the dowry she brought in that is not intact. However, she gets back what is intact. Even one who was Mezanah does not lose this, for her property was not Mezanah (Kesuvos 101b)!

Rosh (7:9): (Overes Al) Das Moshe is when she makes him transgress. If she transgresses other Aveiros, e.g. she eats Isur, she does not forfeit her Kesuvah. Das Yehudis forfeits her Kesuvah because we are concerned for Zenus.

Ran (DH Gemara): She forfeits her Kesuvah only if she fed to him Isur, not for just intending. The Ro'oh says that it is even for intent. He learns from 'Ma'achilaso' (she feeds him).

Hagahos Ashri: If she takes vows that he can annul, it is better to anger her in order that she will tell them to him and he can annul them, like R. Meir says. All agree that he may divorce her for free (without a Kesuvah) if he wants. Transgressing a Cherem or Shevu'ah is Das Moshe. This is like transgressing vows. He can divorce her (against her will). without consent of the congregations. The Gemara asked whether or not one may keep her, but obviously he may divorce her. R. Gershom did not decree in such a case. If a wife goes out with uncovered hair, weaves in public with her elbows exposed, or bathes where men bathe, one who does not divorce her is called a Rasha (Gitin 90a).

Rambam (Hilchos Ishus 24:10): If a wife was Overes Al Das Moshe or Yehudis, she does not get Ikar or Tosefes Kesuvah or any stipulations of the Kesuvah. She gets what remains of her dowry and leaves. Her husband need not compensate for what decreased in value or was lost.

Rambam (11): Das Moshe is going out in the market with uncovered hair, taking vows or oaths and transgressing them, having Bi'ah with him when she is Nidah, not separating Chalah, or feeding to him Isur. We need not say that this applies to feeding to him vermin and Neveilos. It is even for feeding to him untithed food.

Question: Overes Al Das Moshe is vowing and not fulfilling. Why do R. Meir and R. Yehudah allow one to divorce for free just for vowing?

Answer (Tosfos 71a DH v'Im): We are more stringent about vows of affliction, like we find regarding one who married a woman and found that she has vows.

Poskim

Shulchan Aruch (EH 115:1): If a wife was Overes Al Das Moshe, she leaves without a Kesuvah. This is feeding to him untithed food or any other Isur, or having Bi'ah with him when she is Nidah, and he found out afterwards.

Chelkas Mechokek (1): If he feeds to her Isur, or takes vows and transgresses them, he must divorce her and pay a Kesuvah.

Beis Shmuel (1): When he transgresses vows, she can demand to be divorced only if she says that she needs children for her old age.

Chelkas Mechokek (2): Nowadays, Ma'aser is only mid'Rabanan, and he could separate and not rely on her. All the more so feeding to him other Isurim is Das Moshe. It is not clear whether or not making him transgress other matters is Das Moshe. E.g. he relied on her to place an Eruv or burn Chametz, and transgressed because she did not do so.

Beis Shmuel (2): If they only touched while she was Nidah, this is not Das Moshe.

Shulchan Aruch (ibid.): This is only if he ate Isur due to her. If she just wanted to feed to him Isur, she does not forfeit her Kesuvah.

Shulchan Aruch (3): If she takes vows and transgresses them, she leaves without a Kesuvah.

Chelkas Mechokek (6): If she does other Aveiros he cannot divorce her for free. Vows are different, since it causes her children to die. The Terumas ha'Deshen (68) is unsure whether or not this applies to a woman unable to have children. Perhaps it does, for she could have children miraculously. However, nowadays men and women are wanton about vows, so one must be very careful before divorcing a woman for free due to vows, especially if she cannot have children without a miracle.

Rema: The same applies if she transgressed a Shevu'ah or Cherem. If she brings witnesses that also he transgresses vows, oaths or Cherem, she does not forfeit her Kesuvah even if she transgresses.

Beis Yosef (DH v'Chasuv bi'Seshuvas): If also he transgresses, he shows that he does not want children, so this is no reason to divorce her for free.

Darchei Moshe (2): He can divorce her for free if she is Overes Al Das in other matters.

Beis Shmuel (7): If he eats Isur, he cannot divorce her for free for feeding to him Isur. However, if he transgresses vows, we cannot assume that he also eats Isur, or vice-versa.

Rema (ibid.): If she became an apostate and repented, she is not Overes Al Das.

Beis Shmuel (1): The Rosh (Teshuvah 32:3) says that Das Moshe is only when there is concern for Zenus. However, perhaps this is different, for there will be skepticism about the children of a woman who lived with Nochrim, and perhaps it is dangerous for her husband to live in that area.

Shulchan Aruch (5): All of these do not receive Ikar Kesuvah, stipulations of the Kesuvah or Tosefes. She gets what remains of the Nichsei Melug and Nichsei Tzon Barzel. She cannot make her husband pay for what was consumed, stolen or lost.