Ketubot 89B

יכול למימר: גירשתיה ונתתי לה כתובתה.

he can also say: I divorced her and gave her the payment of her marriage contract.

הא מדקתני סיפא: רבן שמעון בן גמליאל אומר: מן הסכנה ואילך אשה גובה כתובתה שלא בגט, ובעל חוב שלא בפרוזבול. בדאיכא עדי גירושין עסקינן. דאי ליכא עדי גירושין, במאי גביא?

The Talmud asks: From the fact that the last clause of the Mishnah teaches that Rabban Shimon ben Gamliel says: From the time of danger and onward, a woman collects payment of her marriage contract without a bill of divorce, and a creditor collects payment without a prosbol, apparently we are dealing with a case when there are witnesses to the divorce. As, if there are no witnesses to the divorce, with what proof does she collect the marriage contract? The Mishnah must be referring to a case where there are witnesses present, and therefore the husband cannot claim that he never divorced her.

אלא כולה רבן שמעון בן גמליאל היא, וחסורי מיחסרא והכי קתני: הרי אלו לא יפרעו. במה דברים אמורים: כשאין שם עדי גירושין, אבל יש שם עדי גירושין ⁠— גביא תוספת. ועיקר, אי מפקא גיטא ⁠— גביא, ואי לא מפקא גיטא ⁠— לא גביא.

Rather, the Talmud rejects the previous explanation and explains: The entire Mishnah is according to the opinion of Rabban Shimon ben Gamliel, and the Mishnah is incomplete and is this is what it is teaching: These debts may not be collected. In what case is this statement said? It is when there are no witnesses to the divorce present there. However, if there are witnesses to the divorce present there, she collects the additional sum listed in the document and not the main sum, lest she later produce the bill of divorce and demand payment a second time. And as for the main sum of the marriage contract, if she produces a bill of divorce, she collects it. But if she does not produce a bill of divorce, she does not collect it.