Mishnayos Shevuos Perek 6 Mishnah 2

The mishna discusses other cases where the defendant denies an entire claim. In a case where one said to another: I have one hundred dinars in your possession, and the latter said to him: Yes, I acknowledge that claim; and the next day the claimant said to him: Give the money to me, and the defendant responded: I already gave it to you, he is exempt. But if he responded: Nothing of yours is in my possession, i.e., he denies that a debt ever existed, he is liable to pay, as he already admitted that he owed him the amount. In a case where the claimant said: I have one hundred dinars in your possession, and the defendant said to him: Yes, to which the claimant responded: Give the money to me only in the presence of witnesses, then if the next day the claimant said to him: Give the money to me, and the defendant responded: I already gave it to you, he is liable to pay, as he is required to give it to him in the presence of witnesses, and he cannot prove that he did so.

מָנֶה לִי בְיָדֶךָ, אָמַר לוֹ בִּפְנֵי עֵדִים הֵן. לְמָחָר אָמַר לוֹ תְּנֵהוּ לִי. נְתַתִּיו לָךְ, פָּטוּר. אֵין לְךָ בְיָדִי, חַיָּב. מָנֶה לִי בְיָדֶךָ, אָמַר לוֹ הֵן, אַל תִּתְּנֵהוּ לִי אֶלָּא בְעֵדִים. לְמָחָר אָמַר לוֹ תְּנֵהוּ לִי, נְתַתִּיו לָךְ, חַיָּב, מִפְּנֵי שֶׁצָּרִיךְ לִתְּנוֹ לוֹ בְעֵדִים: