Reference for Bava Metzia 9:17

דתנן מנה לי בידך אין לך בידי פטור ואמר רב נחמן משביעין אותו שבועת היסת

Abaye, however, answered him: If [the law were] valid, would [the shepherd be allowed to] swear? Is he not a robber?<span class="x" onmousemove="('comment',' Who is likely to commit perjury, hence cannot be given an oath. R. Hiyya's law refers to a debt, or pledge, which the defendant denies, not because he has misappropriated it, or used it for himself, but because he does not find it convenient to repay or replace it just then, and intends to do so later. He therefore cannot be regarded as a robber. ');">¹⁶</span>

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