Reference for Yevamot 178:3
ואם אין קדוש נשיאות חטא למה מיכן לתורם מן הרעה על היפה שתרומתו תרומה
— Here<span class="x" onmousemove="('comment',' Where unclean produce was used as terumah for clean. ');"><sup>7</sup></span> it is different, since Pentateuchally the <i>terumah</i> is valid, in accordance with the view of R. Elai; for R. Elai stated: Whence is it inferred that if one separates <i>terumah</i> from an inferior quality for a superior quality, his <i>terumah</i> is valid? It is written, And ye shall bear no sin by reason of it, seeing that ye have set apart from it the best thereof.<span class="x" onmousemove="('comment',' Num. XVIII, 32. ');"><sup>8</sup></span> [Now, this implies that if you do not set apart from the best but of the worst you shall bear sin]; if, [however, the inferior quality] does not become consecrated, why [should there be any] bearing of sin?<span class="x" onmousemove="('comment',' Surely no wrong has been done where one's action is null and void and other terumah has to he given! ');"><sup>9</sup></span>