Reference for Bekhorot 119:26

אילו היה תמורה לא היה קרב

WERE A SUBSTITUTE, IT WOULD NOT HAVE BEEN SACRIFICED.<span class="x" onmousemove="('comment',' The eleventh is not the substitute for the tenth, for had it been a substitute it would not have been offered up, for Scripture says: Thou shalt not redeem, they are holy (Num. XVIII, 17) . And we deduce thus: They (themselves) are holy but not their substitutes. And although the text refers to the first-born, we derive the case of tithe therefrom (Rashi) . The fact that the eleventh is offered up as a peace-offering proves therefore that it cannot be a substitute and that its holiness is in its own right.');">²²</span>

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