TWO THINGS WHICH CANNOT TAKE EFFECT ONE AFTER THE OTHER
Question: What is Rav's reason?
Version #1 - Answer (Rabah): He did not designate [a particular four Amos, therefore he did not acquire Shevisah].
Version #2 - Answer (Rabah): He holds that if one tries to simultaneously do two things, one of which cannot take effect after the other, neither takes effect. (He tried to make every four Amos under the tree his Shevisah.)
Question: What is the difference between these answers?
Answer: They argue about one who said that four Amos among eight should be his Shevisah;
He did not designate [a particular four Amos]. According to Version #2 it works, for he said that only four Amos should be his Shevisah.
(Rabah): If one tries to do simultaneously two things that cannot take effect one after the other, neither takes effect.
Question (Abaye - Beraisa): If one separates too much Ma'aser, his produce is permitted, but the Ma'aser is messed up. (Some is really Chulin. If Terumas Ma'aser is taken from the Ma'aser, perhaps some is invalid!)
According to Rabah, since one cannot take Ma'aser twice, taking extra Ma'aser at once should do nothing!
Answer (Rabah): Ma'aser is different, for it can be taken halfway. he can make half of a fruit Ma'aser. (Therefore, if he tries to take two or three times as much as he should, it takes effect. Half or a third of every fruit separated becomes Ma'aser.)
Question: Ma'aser Behemah cannot be taken halfway [and one cannot Mekadesh two animals out of 10], but when two animals leave together, it takes effect!
(Rava): If two animals came out together as the 10th [and 11th], one is Ma'aser, the other is the 11th (i.e. Chulin).
Answer: Ma'aser Behemah is different, since it can be taken twice through a mistake:
(Mishnah): If one [was counting animals leaving the pen in order to take Ma'aser, and he] mistakenly called the ninth 'Asiri' (10th), he called the 10th 'ninth', and called the 11th 'Asiri', all three are Kadosh.
Question: One cannot be Makdish [breads of] a Todah (thanksgiving offering) mistakenly, nor can he Makdish extra breads [yet if one tries this, some say that 40 become Kodesh]!
(Chizkiyah): If a Todah was slaughtered with intent to be Mekadesh 80 breads, 40 of them become Kodesh;
(R. Yochanan): They are not Kodesh.
Answer (R. Zeira): If he said '40 of the 80 breads should become Kodesh', all agree that 40 become Kedoshim;
If he said '[even] 40 should not become Kodesh unless all 80 become Kodesh', all agree that none become Kodesh;
They argue when he did not specify. Chizkiyah holds that [he wants only 40 to become Kedoshim.] He brought extra in case some of the 40 will become lost or Tamei. R. Yochanan holds that he wants all 80 to become Kodesh.
WHAT IS CONSIDERED SPECIFYING A PLACE?
(Abaye): [According to Rav, according to Version #1], the Mishnah is only when there are [at least] 12 Amos under the tree - if not, it is as if he specified [the middle four Amos, part of his Shevisah is surely within them].
Objection (Rav Huna brei d'Rav Yehoshua): He did not specify the middle four Amos. Perhaps he specified four Amos on either end [and they do not overlap]!
(Rav Huna brei d'Rav Yehoshua): Rather, the Mishnah is only when there are [at least] eight Amos under the tree. If there are only seven, it is as if he specified [the middle Amah, it is surely part of his Shevisah].
A Beraisa supports Rav, and another Beraisa supports Shmuel.
Support (for Rav - Beraisa #1): If one was traveling and it was [getting] dark, and he saw a fence or tree and said 'my Shevisah is under it', his words have no effect;
If he said 'my Shevisah is at Ploni (a particular place)', he may walk to it, traverse it (i.e. it is more than four Amos), and another 2000 Amos outside of it.
This is only if he specified a place demarcated (by Mechitzos), such as a mound 10 Tefachim tall and between four [by four] Amos] and Beis Sa'atayim, or a valley 10 Tefachim deep and between four Amos and Beis Sa'atayim. However, if he declared Shevisah in a place that is not demarcated, he has only four Amos.
If Reuven knew a particular place and Shimon did not, Shimon says 'my Shevisah will be with Reuven', and Reuven says 'my Shevisah is at Ploni'.
This helps [even if it is not demarcated] if he specified four Amos in the place. if not, he may not move [outside his four Amos, for he did not want to acquire Shevisah here, and he did not acquire in the place he wanted].
Suggestion: This refutes Shmuel!
Rejection: The case is, there are 2004 Amos from his feet to the trunk. If his Shevisah would be on the other side, it is outside his Techum [and invalid]. Therefore, if he did not specify, he may not move.
Support (for Shmuel - Beraisa #2): If one erred and was Me'arev in two directions, because he thought that this is permitted, or he told his slaves to be Me'arev for him, and one was Me'arev in the north and the other in the south:
The Eruv in the south limits him in the north. (He may go only 2000 Amos north of the Eruv.) The Eruv in the north limits him in the south.
If the Eruvin are at the extremes [2000 Amos to the north and 2000 to the south], he may not leave his house [to the north or south. According to R. Chanina ben Antigonus, who gives only 2000 circular Amos, he may not leave his house at all, for the Techumim overlap only in his house. The same applies according to Chachamim, if the Eruvin are in the extreme northeast and southwest corners, or the southeast and northwest corners.]
Suggestion: This refutes Rav [who says that one who did not specify his Shevisah has only four Amos! Rav cannot rely on Beraisa #1, for we were able to explain it according to Shmuel. We do not say that Tana'im argue unless we must.]
Defense of Rav: Rav is a Tana. He argues with the Beraisa.