It is in accordance with the opinion of Rabbi Meir, who says that it is prohibited for a man to remain living together with his wife for even one hour without her having a marriage contract.

(15) If a man seduces a virgin for whom the bride-price has not been paid, and lies with her, he must make her his wife by payment of a bride-price. (16) If her father refuses to give her to him, he must still weigh out silver in accordance with the bride-price for virgins.

“Mohar” means ketuba…“He weighs out silver,” but we have not learned how much. Behold I derive it [from logical comparison], it says here “silver” and it says there “silver” (Devarim 22:29). Just as there it is “fifty”, so here it is fifty…

מהר ימהרנה HE SHALL SURELY GIVE HER THE MARRIAGE PRICE — He shall assign her a marriage portion as is the practice of a man to do to his wife, i. e. he shall write her a Ketuba (marriage contract providing for a marriage portion) and shall marry her (Mekhilta).

According to Rabban Shimon ben Gamliel who said that the marriage contract of a woman is an obligation by Torah law.

As Rabban Shimon ben Gamliel says: The marriage contract of a widow is not an obligation by Torah law but is an ordinance by rabbinic law.

…For the ketuba is rabbinic. But the explanation of mohar is the things that a man sends to his betrothed, silver and gold articles and clothing for the needs of the chuppa and nissuin. And they are what are called sivlonot in the language of the sages…For the groom hurries [memaher] and sends this gift in advance, and afterwards he comes to the house of his father-in-law to make the nissuin or the simcha, as the sages mentioned, “the feast of sivlonot” (Pesachim 49a)…

Since it is a rabbinic ordinance and not a Torah obligation, she may collect only from the husband’s land of the most inferior quality.

For even Rabban Shimon ben Gamliel, who said in the last chapter of Ketubot (110b) that a woman’s ketuba is on a Torah level, didn’t [mean] it was really on a Torah level, but that it has support from the Torah…

…Since God in the Torah uses the language of mohar, Rabban Shimon ben Gamliel derives from it that a betula is entitled to mohar from the Torah. But it has no set amount from the Torah; rather, it is according to what they [the couple] desire, or according to what the sages agree on…

(2) With regard to a virgin, her marriage contract is two hundred dinars, and with regard to a widow, her marriage contract is one hundred dinars.

(8) One who possesses two hundred zuz, may not take gleanings” the forgotten sheaf, peah or the poor man’s tithe.

The ketuba is payment for virginity [demei betulim], therefore it is impossible that he not leave her a maneh [100 zuzim], which is the payment for virginity…

He answered them, is that dependent on the hymen? But the adult has no hymen and her ketubah is 200! the virgin widow has a hymen and her ketubah is a mina! What is the reason? The adult still has all her grace; the virgin widow has lost her grace.

Rav Shmuel bar Unya says in the name of Rav: A woman is raw material, like a vessel that has not been completed, and makes a covenant, becoming truly connected, only to the one who made her a vessel through her first act of sexual intercourse, as it is stated: “For your Maker is your husband, the Lord of hosts is His name” (Isaiah 54:5).

…Before she has had relations, she does not have the capacity for reproductive activity, like something that is unformed….Similarly to what they said above, that the male has satisfaction only from his first wife, he said here that the female also forms a covenant only with her first husband, who made her a receptacle,…as it is written (Hoshea 2:9): “I will go [back] to my first husband,” for He made us [the Jewish people] a receptacle with capacity for the activity of Torah. And before the giving of the Torah, Israel were merely like something unformed…

That opinion is also taught in a baraita: At first they would write for a virgin two hundred and for a widow one hundred dinars, and they would grow old and would not marry women, since the women were concerned that their marriage contract money would be wasted or lost, and they had no guarantee that it would be collected. The Sages therefore instituted an ordinance that they should place it, the sum of the marriage contract, in her father’s house, thereby ensuring its safekeeping. And still problems arose, as when he was angry at his wife, he would say to her: Go to your marriage contract, as it was too easy for them to divorce. Therefore, the Sages instituted an ordinance that they would place it in her father-in-law’s house, i.e., in her husband’s house. And wealthy women would craft their marriage contract money into baskets of silver and of gold, while poor ones would craft it into a large vessel for the collection of urine, as their marriage contract was large enough only for a small vessel. And still, when he was angry at her he would say to her: Take your marriage contract and leave, until Shimon ben Shataḥ came and instituted an ordinance that he does not actually give her the money for her marriage contract. Rather, he should write to her: All my property is guaranteed for her marriage contract, and it is not localized to a particular place or object. Consequently, he would need to sell some of his property if he wished to divorce her, and would therefore think carefully before undertaking such a drastic course of action.

The Rabbis maintain: What is the reason that the Sages instituted a marriage contract for the woman? They instituted it so that she will not be inconsequential in his eyes, enabling him to easily divorce her.

The ketuba of a woman is on account of favor [china].

On account of favor – That men would find favor [china] in the eyes of women and they [women] would marry them.

Rabbi Meir says: It is prohibited to do this, as anyone who reduces the amount of the marriage contract to less than than two hundred dinars for a virgin or one hundred dinars for a widow, this marital relationship amounts to licentious sexual relations because it is as if he did not write any marriage contract at all.

But nevertheless since he said to her: You have only one hundred dinars, she does not rely on the marriage contract and does not see it as a true marriage, and therefore the intercourse becomes licentious sexual intercourse.

…A person isn’t publicly known by his mother’s name as he is by his father’s name, with which they call him to the Torah and with which he signs. And the great rabbis Abba Shaul ben Imma Miryam and Rav Mari bar Rachel and Rav Shimon ben Pazi, were outliers in using such a name, and not everyone who wishes to take his mother’s name can take it. In any case, it is possible that we can use it as a distinguishing sign when there are “two Yosef ben Shimons” [examples of identical names that need to be distinguished], [or when] the chinuch [education] from the mother is well known—like Rav Shmuel Eidels. Or like Chavot Yair, who was called this in the language of the common man on account of his grandmother Chava, who raised him. I further found this in the work Get Pashut 129:51; nevertheless, with a person who does not know their father’s identity or a foundling, he [Get Pashut] permitted from the outset to write the name of his mother…

It seems that the reason to mention the mother is because a woman’s part in raising her children for chuppa is no less than her husband’s, or even more. And although writing the names in the ketuba isn’t for purposes of honor, in any event, it will be considered as an honor to her to be mentioned within it, especially according to our custom, for we read the ketuba out loud…There is no concern of u-vchukoteihem [following idolatrous ordinances] in mentioning the mother, for we have found many instances in the books of Melachim and Divrei Ha-yamim of “and king such-and-such dies and such-and-such became king in his stead, and his mother’s name was such-and-such.” Behold, it is not from them [the non-Jews] that we learn this…

How much is the value of the ketuba? For a betula 200, and for a widow a maneh [100]. And that of each of them is kesef medina [alloyed coins], so the ketuba of a betula is 37.5 dirhams [coins] of pure silver.

Rema:…But according to the opinion of some authorities, the 200 of the betula and maneh of the almana are valued in the Torah’s zuzim, which is eight times more….And they wrote that therefore they had the custom to write in the ketuba, “that is fit for you from the Torah” [Rabbeinu Tam]….

Nichsei Tzon Barzel – That are valuated in her ketuba: “And this nedunya [dowry] that she brings him from her father’s house.” And he [the chatan] takes upon himself financial responsibility to return them to her in the event that she leaves the marriage.

Although they said as a principle that a virgin collects two hundred dinars as payment for her marriage contract and that a widow collects one hundred dinars, if the husband wishes to add even an additional ten thousand dinars, he may add it.

…The witnesses only sign the ketuba after the chatan has made a kinyan before them…

(6) And these are examples of women who may be divorced without payment of their marriage contract: A woman who violates the precepts of Moses, i.e., halakha, or the precepts of Jewish women, i.e., custom. The Mishna explains: And who is categorized as a woman who violates the precepts of Moses? This includes cases such as when she feeds him food that has not been tithed, or she engages in sexual intercourse with him while she has the legal status of a menstruating woman, or she does not separate a portion of dough to be given to a priest [ḥalla], or she vows and does not fulfill her vows. And who is considered a woman who violates the precepts of Jewish women? One who, for example, goes out of her house, and her head, i.e., her hair, is uncovered; or she spins wool in the public marketplace; or she speaks with every man she encounters..

One can say that — whether she violates a real Torah-level mitzva, or whether she violates the Jewish practice that the daughters of Israel conduct themselves modestly — the woman leaves [the marriage] without a ketuba. Thus [the mishna] specifies what she violates and causes him [her husband] to violate among the mitzvot of the Torah. Therefore there [in the mishna] the intended meaning of dat Moshe is real[ly a Torah prohibition], and dat Yehudit is modest Jewish conduct.

Rema: Rabbeinu Gershom decreed that [a man] cannot divorce a woman without her knowledge...even if he wants to give her the ketubah, he cannot divorce her nowadays without her knowledge (Smak Siman 184).

(3) If he wrote her a ketuba, and it was lost, or she waived it,…he needs to write her another with the ikkar ketuba. For ‘it is forbidden for a man to remain with his wife for even one hour without a ketuba’…

Rema:…At this time, in these lands, where we do not divorce a woman against her will because of the edict of Rabbeinu Gershom,…it would be possible to be lenient regarding the writing of the ketuba. But the custom is not so, and one should not do differently…