Mishnayos Yevamos Perek 15 Mishnah 3

Beit Shammai say: A woman who testifies that her husband died may marry, and take the money guaranteed in her marriage contract. Beit Hillel say: She may marry, but she may not take her marriage contract, as qualified witnesses are required for monetary matters. Beit Shammai said to them: If you have permitted a woman potentially forbidden to him, which is a relatively stringent prohibition, based merely upon her own testimony, will we not permit a monetary matter, which is more lenient, as the money can be returned and this sin does not entail such a severe punishment? Beit Hillel said to them: This is no proof, as we find that the brothers do not come into the inheritance from the deceased brother based on her testimony. Evidently, although this testimony is accepted with regard to forbidden sexual relationships, it is not effective for monetary matters. Beit Shammai said to them: But we can learn this halakha from the scroll of the marriage contract, as every husband writes for her that: If you marry another man, take what is written for you in this contract. This shows that her right to receive the money of her marriage contract is dependent upon her eligibility to remarry. In this case, as she is deemed credible when she says her husband died and she may marry again, she is likewise entitled to the money of the marriage contract. And Beit Hillel again retracted their opinion, and decided to teach in accordance with the opinion of Beit Shammai.

בֵּית שַׁמַּאי אוֹמְרִים, תִּנָּשֵׂא וְתִטֹּל כְּתֻבָּתָהּ. בֵּית הִלֵּל אוֹמְרִים, תִּנָּשֵׂא וְלֹא תִטֹּל כְּתֻבָּתָהּ. אָמְרוּ לָהֶן בֵּית שַׁמַּאי, הִתַּרְתֶּם עֶרְוָה חֲמוּרָה, לֹא תַתִּירוּ אֶת מָמוֹן הַקַּל. אָמְרוּ לָהֶן בֵּית הִלֵּל, מָצִינוּ שֶׁאֵין הָאַחִים נִכְנָסִים לַנַּחֲלָה עַל פִּיהָ. אָמְרוּ לָהֶם בֵּית שַׁמַּאי, וַהֲלֹא מִסֵּפֶר כְּתֻבָּתָהּ נִלְמֹד, שֶׁהוּא כוֹתֵב לָהּ, שֶׁאִם תִּנָּשְׂאִי לְאַחֵר, תִּטְּלִי מַה שֶׁכָּתוּב לִיכִי. וְחָזְרוּ בֵית הִלֵּל לְהוֹרוֹת כְּדִבְרֵי בֵית שַׁמָּאי: