We are reaching the final Mishnah in the seventh chapter of tractate Bava Kamma. Until now, the tractate has dealt mostly with laws regarding domesticated and wild animals, and at the conclusion of the chapter, the Mishnah presents a collection of rabbinic laws and enactments by the Sages that limit and regulate the way a person raises animals. This is a collection of various cases that are unrelated to one another.
"Ein megadlin behemah dakkah b'Eretz Yisrael" - One may not raise small livestock in Eretz Yisrael:
It is forbidden to raise small livestock, meaning flocks of goats and sheep, in Eretz Yisrael - and as will be explained, the prohibition applies to settled areas. At the foundation of this enactment is the desire of the Sages to ensure the fulfillment of the mitzvah of settling Eretz Yisrael, and to allow the land to sustain as large a population as possible. Land is a limited resource: it can be allocated for agricultural crops that provide food for people, and it can be allocated for pasture. When animals are raised, they eat the growing grain, and it turns out that the agricultural output of the land decreases. Although there is a benefit in increasing livestock, allocating more land for agriculture allows a larger population to be sustained, and therefore the Mishnah forbade raising goats and sheep.
Two allowances in the Mishnah:
"Aval megadlin b'Surya" - in Syria it is permitted to raise goats and sheep without any restriction. Syria is the region north of Eretz Yisrael, around the Euphrates River, which was conquered by King David during the First Temple period. This conquest did not expand the halachic borders of Eretz Yisrael, and the sanctity of the Land does not apply to it. There is a discussion among the Rishonim regarding the reason for this, but the fundamental point is that the conquest was not carried out with the full participation and approval of the Sages, but rather as an individual act. Thus, the political borders expanded up to Syria, but the sanctity of the Land did not reach there. This is similar to the borders of the State of Israel today, which include Eilat, even though Eilat is not part of Eretz Yisrael and was never sanctified with its holiness. Since living in Syria does not fulfill the spiritual virtues of living in Eretz Yisrael, the Sages did not see value in restricting the raising of animals there; on the contrary, if the population cannot survive there, they will be forced to move south and arrive in Eretz Yisrael itself.
"Uvamidbaros sheb'Eretz Yisrael" - in the deserts of Eretz Yisrael it is permitted to raise flocks of sheep and goats without restriction. Since there is no settlement there, these lands are not designated for agricultural use anyway, and grazing flocks there, outside the boundaries of populated centers, does not diminish the Land's ability to sustain its population.
It is worth noting that large livestock as well - cows, horses, and mules - eat from the agricultural produce and reduce the amount of food that can be produced in the Land. Nevertheless, the Sages did not forbid raising them, because these animals are beasts of burden and work animals that are used for agriculture itself. The Sages did not want to enact a decree that the public cannot abide by, and any decree that the public cannot abide by is not binding. Therefore, they only forbade raising goats and sheep, and not the other types of work animals.
"Ein megadlin tarnegolim b'Yerushalayim mipnei hakodashim" - One may not raise chickens in Jerusalem because of the kodashim:
One may not raise free-roaming chickens in Jerusalem, as they search for their food in the garbage dumps around the city, a place where all sorts of things are found, including dead creeping animals (sheratzim). The concern is that the chickens pecking in the dumps will bring back small bones with them, and even a bone the size of a barley grain from a sheretz is a source of tumah. Jerusalem is full of people eating kodashim - anyone who makes the pilgrimage and brings a peace offering or thanksgiving offering eats minor kodashim inside the city walls - and therefore the Sages were concerned about small, unnoticeable sources of tumah infiltrating the city by means of the chickens. This prohibition applies to free-roaming chickens, but chickens kept in a closed coop are permitted.
A source for this can be seen in the Mishnah in tractate Chullin, at the end of the first chapter, which mentions the rooster's crow (keriat hagever). From here we see that there were chickens in Jerusalem, but they were kept inside a closed coop and could not roam and bring tumah.
"Velo kohanim b'Eretz Yisrael mipnei hateharot" - Nor may kohanim anywhere in Eretz Yisrael because of the pure foods:
Even outside of Jerusalem, kohanim are forbidden to raise chickens anywhere in Eretz Yisrael. Eating kodashim, and even minor kodashim, is not possible outside the walls of Jerusalem, but the kohanim receive the gifts of the great Terumah, Terumah of the tithe, and challah, and they have a Torah obligation to maintain their purity. Even if there is no Terumah in his house at that time, if the kohen raises chickens in his vicinity, they might bring a requisite measure of tumah with them, and the kitchen utensils - the bowls and knives - will become impure; subsequently, when he receives his Terumah, he will inadvertently defile it. Outside of Eretz Yisrael, this is not a problem: there is no Terumah outside the Land, and even the challah that is observed there is impure from beginning to end, so this is not relevant to our matter.
"Ein megadlin chazirim bechol makom" - One may not raise pigs anywhere:
A Jew is forbidden to raise pigs anywhere, and this is a rabbinic law. By Torah law, there is already a prohibition against raising non-kosher animals as a food source, even if they are sold to non-Jews, and therefore raising pigs to sell their meat is forbidden regardless. However, raising pigs for other commercial purposes, such as for their skins, is not forbidden by the Torah - and it is regarding this that the Sages enacted a decree to prohibit it.
Why were pigs specifically prohibited? Because of an incident that occurred. At the end of the Hasmonean period, two brothers, Aristobulus and Hyrcanus, fought for control over Jerusalem, one laying siege to the other: one was outside the walls and the other was inside. Even though a military campaign was underway, the people on the outside would supply the people on the inside with two sheep every day, in a box that was hoisted over the walls, so they could offer the daily Tamid sacrifices in the Temple. Until one day they said: As long as we supply them with the Tamid sacrifices, we will not win this war, because God is helping them. In a brazen and repulsive act, they sent a pig in the box instead of the sheep, and the Gemara says that the pig dug its hooves into the walls of Jerusalem and the entire Land of Israel quaked. Following that terrible event, the Sages arose and decreed: Jews may no longer raise pigs anywhere.
"Lo yegadel adam et hakelev ela im ken hayah kashur beshalshelet" - A person may not raise a dog unless it is tied with a chain:
The Mishnah is not dealing with a prohibition against keeping a small, harmless pet. The reference is to large, intimidating dogs that bark and might bite, frighten people, and even cause a woman to miscarry out of fear, Heaven forbid. Therefore, it is forbidden to keep this type of dog unless it is tied with a metal chain, in such a way that no one is afraid of it.
"Ein porsein nishbin layonim ela im ken hayah rachok min hayishuv sheloshim ris" - One may not set snares for doves unless it is thirty ris away from the settlement:
One may not set traps to catch doves unless they are placed far from an inhabited area. People raised doves for various purposes - for food, fertilizer, communication, and sacrifices - and even though a wild dove is ownerless, and anyone has the right to acquire it just as they would acquire a fish in the sea, many doves are privately owned and roam in search of food. Someone who spreads a net near a settlement might catch his fellow's dove, which is robbery. Therefore, the Sages enacted to distance the nets from populated centers, so that any bird caught will presumably be ownerless and not privately owned.
As for the measure of the distance - thirty ris (in other versions: rus) - there are seven and a half of these in a mil, meaning that thirty ris is four mil. One mil is two thousand amos. The origin of the word is identical to the origin of the English word mile, from the Latin for a thousand (as in the words millipede - a thousand legs - and millimeter), since it referred to a thousand paces of a Roman soldier; however, the Sages did not measure in paces but in amos, hence the measure of two thousand amos. Although the name is similar to a mile, the measure is much closer to a modern-day kilometer, and thus bird traps must be placed at a distance of about four kilometers outside the city, to ensure that the trapper does not catch privately owned birds.
In summary: This Mishnah compiles rabbinic enactments regarding raising animals: the prohibition of raising small livestock in the Land of Israel to protect the settlement of the land, and the permission to do so in Syria and in the deserts; the permission to raise large livestock because the public cannot withstand its prohibition; the prohibition of raising chickens in Jerusalem because of consecrated items, and throughout the Land of Israel for kohanim because of purity laws; the prohibition of raising pigs anywhere following the incident of the Hasmoneans; the prohibition of raising a harmful dog that is not tied with a chain; and the prohibition of spreading traps for doves near a settlement out of concern for robbery.
With this, we have concluded the seventh chapter of Tractate Bava Kamma and the topics discussed within it. In the eighth chapter, we will move on to a completely new topic - the laws of one who injures his fellow.