Bikkurim, Chapter Two, Mishnah Five
Having completed comparing bikkurim, terumah and maaser with one another, the Mishnah now turns its attention to comparing terumat maaser with bikkurim and maaser. Terumat maaser is the terumah that the Levite takes out of the tithe that he receives (see Numbers 18:26).
The terumah of tithe is like bikkurim in two ways, and like terumah in two other ways:
1) It may be taken from pure produce for impure produce;
2) And from such produce that is not in close proximity, like bikkurim.
3) And it renders the contents of the threshing-floor forbidden,
4) And it has a prescribed amount like terumah.
Section one: There are two ways in which terumat maaser is like bikkurim. First of all, if one has pure maaser and impure maaser , he can separate terumah from his pure maaser in order to exempt his impure maaser. When it comes to terumah, one cannot do this (see Hallah 1:9; Terumot 2:1).
Section two: If one has two piles of maaser, one that is in close proximity and one that lies further away, he can take terumat maaser from the close pile and thereby exempt the pile that is further away. Again, this cannot be done when it comes to giving terumah (see Hallah 1:9).
Section three: Terumat maaser is similar to terumah in that before one separates terumat maaser he cannot eat the grain that is found on the threshing floor, or other produce found elsewhere (see above mishnah three). Not having taken bikkurim, as we learned, does not render the produce forbidden.
Section four: Terumat maaser is 1/10 of the maaser. This amount is fixed, as is terumah. Bikkurim, as we saw in mishnah three, do not have a fixed amount.