Bava Batra 104B

ואי איכא מילתא יתירא, דהוי לתשעת קבין ⁠– הדרי.

And if after this calculation there is still a surplus in excess of 1/4th-kav per se’a, equal in size to an area required for the sowing of 9 kav of seed, the entire surplus must be returned.

איתיביה רבא לרב נחמן: ״שאם שייר בשדה בית תשעת קבין״⁠ – לאו דזבין ליה כוריים? לא, דזבין ליה כור.

Rava raised an objection to Rav Naḥman: The Mishnah teaches that if the surplus in the field was an area required for the sowing of 9 kav of seed, the buyer returns the land to the seller. Isn’t this the halakha even in a case where he sold him a field measuring two kor? This would seem to indicate that even if the surplus does not exceed 1/4th-kav per se’a, as 1/4th-kav per se’a in a field of two kor is 15 kav, the sole determining factor is whether or not the surplus is equal in size to an area required for the sowing of 9 kav. Rav Naḥman rejects this argument: No, the case in the Mishnah is specifically where he sold him a field measuring one kor.

״ובגנה בית חצי קב״⁠ – לאו דזבין ליה סאתים? לא, דזבין ליה סאה.

Rava raised a further objection to Rav Naḥman: We learned in the continuation of the Mishnah that if the surplus in a garden was an area required for the sowing of a half-kav of seed, the buyer returns the land to the seller. Isn’t this the halakha even in a case where he sold him a garden measuring two se’a? Once again, this would seem to indicate that the surplus is returned to the seller, provided that it is equal in size to the minimum measure of a garden, even if the surplus does not exceed one-half of a kav per two se’a, which is equivalent to 1/4th of a kav per se’a. Rav Naḥman rejects this argument as well: No, the case in the Mishnah is where he sold him a garden measuring a se’a, so that the surplus is proportionately twice as large.