Kilayim, Chapter 5, Mishnah 7. In the previous mishnah we learned that a mixture in a vineyard creates the prohibition of kilei hakerem only when it comes about through the will of the owner of the vineyard, when it is something he has an interest in. Building on that same idea, our mishnah continues and lists cases in which seeds reached the vineyard unintentionally and without his knowledge.
The cases in which the sowing does not create a prohibition:
"Ha'over b'kerem v'naflu mimenu zera'im" - a person walked through his vineyard and seeds fell from him and planted themselves in the ground, seeds that constitute kilayim with the vineyard.
"O sheyatz'u im hazevalim" - the seeds reached the vineyard together with the manure.
"O im hamayim" - the seeds were carried in with the water used for irrigation.
"Hazorea v'si'arato haruach l'acharav" - a person was sowing in another area, in a different field, and the wind swept some of the seed into the field behind him, in a manner he is not aware of.
In each of these cases the mishnah rules "mutar" - it is permitted: even though these are seeds that constitute kilei hakerem, and they have already begun to grow, since it did not happen intentionally, and the owner of the vineyard is unaware of it and has no interest in it, there is no prohibition of kilei hakerem.
"Si'arato haruach l'fanav" - the wind swept it in front of him:
But if the wind swept the seed in front of him, and he is aware of it and did not uproot it, and the seed took root and began to grow, the prohibition takes effect. How does one deal with it? This is the subject of the continuation of the mishnah in the words of Rabbi Akiva, who distinguishes between three stages of growth:
"Im asavim - yofach" - if the seed has grown only to the stage of grass, one must turn the soil over and uproot it, so that it is no longer rooted in the ground.
"V'im aviv - y'napetz" - if it has passed the grass stage and grown into a full plant, but has not yet reached a third of its growth, one must extract the seed from the plant itself.
"Im heivi'ah dagan - tidalek" - if it has reached full growth, or at least a third of its growth, it must be burned and destroyed, and it is all forbidden to derive any benefit from it.
The dispute in the Yerushalmi about the meaning of "y'napetz":
Reish Lakish: "y'napetz" means that he removes the seeds, and they become forbidden, but the straw and the chaff of the plant remain permitted.
Rabbi Yochanan: one must destroy not only the seed, but the entire plant at the aviv stage, since all of it is forbidden to derive benefit from.
At the stage of "heivi'ah dagan" there is no dispute: even Reish Lakish, who permitted the chaff at the aviv stage, before it had grown a third, agrees that once the seed has reached full growth, or at least a third of its growth, which is considered full growth, everything is forbidden to derive benefit from, and even the chaff requires destruction. The entire plant is burned.
In summary: in this mishnah we learned that seeds which reached the vineyard unintentionally - they fell from someone walking through the vineyard, came in with the manure or with the water, or the wind swept them behind him - are permitted, since there is neither will nor awareness involved. But seed that the wind swept in front of him, where the owner knew and did not uproot it, becomes forbidden, and Rabbi Akiva distinguishes between three stages: grass, one turns it over; aviv, one extracts the seed; it produced grain, it is burned. Regarding the meaning of "y'napetz" the Yerushalmi is divided, whether only the seeds become forbidden (Reish Lakish) or the entire plant (Rabbi Yochanan), and at the stage of "heivi'ah dagan" all agree that everything is forbidden to derive benefit from and requires destruction.