Tractate Terumot - Chapter 5 - Mishnah 4 תרומות פרק ה׳ משנה ד׳

A seah of unclean terumah that falls into one hundred seahs of clean terumah: Bet Shammai prohibits, But Bet Hillel permits. Bet Hillel said to Bet Shammai: since clean [terumah] is forbidden to non-priests and unclean [terumah is forbidden] to priests, then just as clean [terumah] is brought up, so too unclean [terumah] can be brought up. Bet Shammai answered them: No! If hullin which is treated more leniently [in that it is permitted to non-priests] allows us to bring up clean [terumah that falls into it], does terumah [which is more stringent in that it is forbidden to non-priests] also allow us to bring up that which is unclean? After [Bet Shammai] had agreed [with Bet Hillel], Rabbi Eliezer said: it should be taken out and burned. But the sages say: it is gone, on account of its being a tiny [portion of the whole mixture].