Reference for Bekhorot 53:6

ותנא מאי טעמא לא קאמר מתנות כהונה

When terumah is consecrated as such, since it is not redeemed, no mistake can be made with it.<span class="x" onmousemove="('comment',' Since everybody is aware that terumah cannot lose its holiness, and therefore the priest on whose behalf the sela' was paid by the Israelite will not mistakenly use it as hullin.');">⁴</span>

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