Kilayim, Chapter Seven, Mishnah Four
In this mishnah and the two that follow, we learn about what happens if one person sows seed in someone elses vineyard or someone puts a vine over someone elses grain. Does this make the grain into kilayim?
1) One who causes his vine to overhang his fellows grain, behold he has caused the grain to be prohibited and he is responsible for it.
2) Rabbi Yose and Rabbi Shimon say: a person does not prohibit [as kilayim] that which is not his own.
Section one: According to the first opinion, when a vine is hung over grain it causes the grain to become kilayim, even if the grain doesnt belong to the person who hung up the vine. Since he has ruined someone elses property, he must pay for the damage he has caused.
Section two: Rabbi Yose and Rabbi Shimon hold that a person cant make kilayim in someone elses vineyard. This is derived from a midrash on Deuteronomy 22:9, which states, Dont seed your vineyard kilayim. From the word your the rabbis learn that this rule applies to one who seeds his own vineyard, and not one who seeds someone elses vineyard.