Related for Sotah 59:12
מטמא אחד ופוסל אחד בתרומה
it creates one further degree of defilement and one of disqualification with the heave-offering;<span class="x" onmousemove="('comment',' There is then a third degree. ');"><sup>12</sup></span>
Mishnah Challah
Rabbi Eliezer says: Hallah may be taken from [dough] that is clean, [in order to exempt] that which is unclean. How [may this be done]? [If one has] clean dough and unclean dough, he takes sufficient hallah out of the [clean] dough whose hallah has not yet been taken, and puts [dough] less than the size of an egg in the middle, in order that he may take off [the hallah] from what is close together. But the sages prohibit.
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