Reference for Shevuot 49:2

רבינא אמר כי קתני מידי דחייל אמידי דבר אכילה הוא שבועה דחיילא אמידי דלאו בר אכילה הוא לא קתני

Rabina said: The Tanna mentions only that which is applicable to foods, but an oath, which can take effect even on that which is not a food, he does not mention. But [he mentions] holy things, which are applicable also to wood and stone! - Well then, he mentions only that which is applicable to that which has substance, but an oath, which can take effect also on that which has no substance, as, for example, T shall sleep', or, I shall not sleep.' he does not mention. <br>

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