Kilayim, Chapter Four, Mishnah Eight
This mishnah deals with a case of a person who planted two or three rows of vines and left a significant gap unplanted in between themhow big does the gap have to be for him to be allowed to plant seeds there?
1) One who has planted two rows [of vines]if there are not eight cubits between them, he may not bring seed there [in the space between the two rows].
2) If there are three [rows]if there are not between one row and its companion sixteen cubits he may not bring seed there.
3) Rabbi Eliezer ben Jacob said in the name of Hananya ben Hakinai: even if the middle row was laid waste and there is not between one row and its companion row sixteen cubits, he may not bring seed there, but if he had planted them [two rows] at the outset, it is permitted [to sow between them] if they are eight cubits [apart].
Section one: If there are more than eight cubits separating the two rows, then they do not join together to form a vineyard. In such a case he may leave six handbreadths space from each row and in the middle plant seed. However, if there are less than eight cubits, then this counts as a vineyard and he cant plant any seed in between.
Section two: If there are three rows of vines, then there has to be a gap of sixteen cubits in between for the rows not to join together and count as a vineyard. We will learn more about this in tomorrows mishnah.
Section three: Rabbi Eliezer ben Jacob distinguishes between a case where there were originally three rows and then the middle row was destroyed and a case where there were originally only two rows. If there were originally three rows and the middle row was destroyed we look at the vines as if the middle one was still there. Hence there must be sixteen cubits between each row of vines in order to plant seeds in between. However, if he originally planted only two rows, then they need to be separated by only eight cubits, as we learned in section one.