Reference for Shevuot 82:2

אמר לך רב אסי אנא כי אמרי היכא דמעיקרא אוזפיה בעדים דלא לדידיה הימניה הכא הא הימניה

R'Joseph taught it thus:<span class="x" onmousemove="('comment',' He had a different tradition as to what R. Judah reported to Samuel in the name of R. Assi.');">³</span> R'Judah said, R'Assi said: If one lends to his neighbour before witnesses, he need not repay him before witnesses; but if he said to him: 'Do not repay me except before witnesses,' he must repay him before witnesses.

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