Ketubot 87B

רבי שמעון אומר: כל זמן שהיא תובעת כתובתה ⁠— היורשין משביעין אותה, ואם אינה תובעת כתובתה ⁠— אין היורשין משביעין אותה.

R' Shimon says: Whenever she claims payment of her marriage contract, the heirs administer an oath to her. And if she does not claim payment of her marriage contract, the heirs do not administer an oath to her.

גמ׳ סבר רמי בר חמא למימר שבועה דאורייתא ⁠— דקא טעין מאתים וקא מודה ליה במאה, הויא ליה הודאה במקצת הטענה, וכל המודה במקצת הטענה ⁠— ישבע.

Talmud: Rami bar Ḥama thought to say that the oath of a woman who vitiates her marriage contract is an oath required by Torah law, which is the oath of one who makes a partial admission, as the husband claims that he paid her 200 and she concedes to him with regard to 100. This is a partial admission of the claim, and the principle is that whoever admits to part of a claim must take an oath according to Torah law to receive the remaining amount.

אמר רבא: שתי תשובות בדבר: חדא ⁠— דכל הנשבעין שבתורה נשבעין ולא משלמין, והיא נשבעת ונוטלת. ועוד: אין נשבעין על כפירת שעבוד קרקעות.

Rava said: There are two answers in the matter, in refutation of your argument: One response is that anyone who is obligated to take an oath that is enumerated in the Torah takes an oath and does not pay. By Torah law, one takes an oath only to exempt himself from payment, and in this case she takes an oath and takes her money. And furthermore, there is a principle that one does not take an oath with regard to a denial of a lien on land. The oaths of the Torah apply only to moveable property, not land. This means that if a claim involves a lien on land of any form, the oath of a partial admission does not apply, and a marriage contract includes a lien on land.