Source and decoding - Ketubot 12b
גְּמָ׳ אִתְּמַר: ״מָנֶה לִי בְּיָדְךָ״, וְהַלָּה אוֹמֵר: אֵינִי יוֹדֵעַ — רַב יְהוּדָה וְרַב הוּנָא אָמְרִי: חַיָּיב, וְרַב נַחְמָן וְרַבִּי יוֹחָנָן אָמְרִי: פָּטוּר.
Gemara: It was stated: If one says, “You owe me one hundred,” and the other says, “I do not know,” Rav Yehuda and Rav Huna say: Liable. Rav Nahman and Rabbi Yohanan say: Exempt.
A maneh is one hundred zuz; matayim is two hundred zuz. First separate the amount claimed from the strength of the claim. In the debt case, the claimant asserts certainty and the defendant expresses uncertainty. Rav Huna and Rav Yehuda favor the certain claim. Rav Nahman and Rabbi Yohanan leave the money with its holder. In the Mishnah, the woman says she was raped after betrothal. The husband places the loss of virginity before betrothal. Although his wording is firm, in this discussion he lacks certain knowledge of when it occurred. The Gemara then distinguishes certainty alone from certainty supported by migo or a presumption.