Reference for Gittin 102:1

הוא דאמר כרבי אליעזר בן יעקב דתניא ר' אליעזר בן יעקב אומר פעמים שאדם נשבע על טענת עצמו כיצד מנה לאביך בידי והאכלתיו פרס הרי זה נשבע וזה הוא שנשבע על טענת עצמו

— He adopted the view of R. Eliezer b. Jacob, as it has been taught: R. Eliezer b. Jacob says, There are times when a man has to take an oath on account of his own plea. For instance: If a man says, 'Your father lent me a <i>maneh</i> and I returned him half of it,' he has to take an oath, this being the kind of person who has to take an oath on account of his own plea. The Sages, however, say that he is on the same footing as one who restores a lost article, and he is exempt [from an oath].<span class="x" onmousemove="('comment',' Shebu. 42a; Keth. 18a. ');">¹</span>

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