1)WHICH CLAUSE DO WE FOLLOW?
(a)(Mishnah #1 - Ben Nanas): If one said 'I sell to you (a Beis Kor) measured by a rope, be it less or more', (the latter clause) 'be it less or more' overrides 'measured by a rope'.
(b)If he said 'be it less or more, measured by a rope', 'measured by a rope' overrides 'be it less or more'.
(c)(R. Aba bar Mamal): Other Tana'im argue with Ben Nanas.
(d)Question: We already know this from a Mishnah!
1.(Mishnah #2): A case occurred in Tzipori in which Levi rented out his bathhouse 'for 12 Dinarim for the year, a Dinar per month' (and it became a leap year). R. Shimon ben Gamliel and R. Yosi ruled that the renter pays half for the added month.
2.(They do not say that the latter clause overrides the former!)
(e)Answer: One might have thought that there, we are not sure if Levi retracted (and wants 13 Dinarim if it will be a leap year), or if he only comes to explain (that rent is due every month, and not at the end of the year, but indeed the rent is 12, even if it will be a leap year), but here surely the seller retracted, and Chachamim would admit to Ben Nanas;
1.R. Aba teaches that this is not so.
(f)(Rav Yehudah citing Shmuel): This (Mishnah #1) is like Ben Nanas, but Chachamim say that the buyer has the lower hand (since we are unsure which clause overrides the other).
(g)Inference: 'This is like Ben Nanas' implies that the Halachah does not follow him.
(h)Contradiction: Rav and Shmuel taught that if Reuven sold to Shimon 'a Kor (of grain) for 30 (Sela'im)', either can retract until all is measured out;
1.If he said 'a Kor for 30, each Se'ah for a Sela', after each Se'ah is measured out, neither can retract. (The latter clause overrides the former. Each Se'ah is a sale by itself!)
(i)Answer #1: Rather, this is like Ben Nanas, and the Halachah follows him.
(j)Question: Shmuel does not rule like Ben Nanas!
1.Shmuel taught that in Mishnah #2, they argue in the middle of the month. If they argue at the beginning of the month, the renter must pay for it, and if they argue at the end of the month, the renter need not pay for it! (The latter clause does not override the former.)
(k)Answer #2: Really, Shmuel says the Halachah does not follow Ben Nanas. Regarding the bathhouse, whoever is Muchzak has the upper hand. (If Reuven already used it in the extra month, Shimon cannot force him to pay. If he did not yet use it, he may not use it without paying.)
(l)(Rav Huna citing bei Rav): If Levi said 'I sell this for Istira (a half Dinar, i.e. 96 Perutos), 100 Ma'os' (and Yehudah agreed), he owes 100 Ma'os;
1.If he said 'I sell for 100 Ma'os, Istira', Yehudah owes Istira.
(m)Question: Rav teaches that the latter clause overrides the former. He already taught this in another way!
1.(Rav): I would say that the renter must pay to use the bathhouse in the added month.
(n)Answer: Had Rav taught only about the bathhouse, one might have thought that there, his reason is not because the latter clause overrides the former, rather, because the latter clause explains the former. (Therefore, he also taught about '100 Ma'os/Istira' to teach that the latter clause overrides the former.)