We are now beginning the second chapter of Tractate Bava Basra, which deals with distancing damages: keeping away phenomena and activities that a person does in his own property, yet they are liable to damage his neighbor's property. The basis of this is rooted in the principle "Her ways are ways of pleasantness, and all her paths are peace" - the way of the Torah is a way of pleasantness and paths of peace, and from here many have learned that a person is not permitted to perform actions even within his own property when they cause damage to his neighbor. Mishnah 1 discusses a number of cases, and each of them stands on its own.
"Lo yachpor adam bor samuch levoro shel chavero" - a person may not dig a pit close to his neighbor's pit:
A person is not permitted to dig a pit for storing water in his property close to his neighbor's pit. The reason: when the cavity in the ground is located too close to his neighbor's cavity, the walls of the neighbor's pit are weakened, cracks form in them, and they are liable to collapse or leak water. Therefore, an obligation to distance is imposed. This law is not limited to digging a pit alone, but applies also to:
"Velo shi'ach" - an elongated trench in the ground.
"Velo me'arah" - a roofed cavity for storing water.
"Velo ammas hamayim" - an irrigation canal.
"Velo nivreches kovsin" - a rectangular pool in the ground for collecting water, used for washing and cleaning clothes.
In all of these, the Mishnah states: "Ella im kein hirchik mikosel chavero sheloshah tefachim vesad besid" - unless he distanced it three tefachim from his neighbor's wall and plastered it with lime. Two obligations are imposed on the digger: to distance it three tefachim from the wall of his neighbor's pit, and also to plaster the walls of the excavation from the inside with lime.
What is the main problem with this excavation?
Some say that the very excavation close to the pit weakens the walls around his neighbor's pit, causing leakage and collapse.
And some say that the problem is water damage: the moisture seeping from the pit spreads, causes mold, and weakens and endangers his neighbor's pit.
There is a practical difference between the opinions. According to Tosafos, who hold that the concern is water damage, a cavity in the ground that has no water at all, which is used merely for storage, would not have this problem. Regardless, in practice both obligations were stated together: the distancing and the plastering. When there is no water in the excavation, it is understood that there is no need for lime; but even according to the one who holds that the problem is not water damage per se, the plastering is required, since without it the water will leak and weaken the walls of his neighbor's pit.
The measurement of the distancing requires explanation: in a pit in the ground, what are its "walls"? Is there not only earth there? Therefore, the Sages established that the three tefachim of earth surrounding the cavity are what is called the wall of the pit. It turns out that the distancing of three tefachim is measured from the edge of the wall, meaning an additional three tefachim beyond the cavity itself. In total, the digger must distance the cavity of his pit six tefachim from the cavity of his neighbor's pit. And this law is the same for a pit, a trench, a cave, an irrigation canal, and a washer's pool.
Distancing materials that damage through heat and corrosion:
The next case deals not with a pit in the ground, but with a wall above the ground, such as a structure built by the neighbor. Here too, even though the person is using his own property, if he places his materials close to his neighbor's wall he will cause him damage. The Mishnah lists materials that damage through heat or through corrosion and oxidation: "Marchikin es hagefes ve'es hazevel ve'es hamelach ve'es hasid ve'es hasela'im" - we distance the grape waste, the manure, the salt, the lime, and the rocks:
"Hagefes" - the grape waste remaining after squeezing them for wine. When organic material is piled up and begins to rot, like a compost pile, it gets hotter and hotter and can reach a temperature of fifty or sixty degrees Celsius, and this heat damages the neighbor's wall.
"Hazevel" - manure. The law is the same. The decomposition process is an exothermic reaction, and this can be felt even in a household garbage bag where food waste has been placed: the next day its contents are warm. Here too, the concern is the production of intense heat that damages the wall.
"Hamelach" - salt. Salt does not emit heat, but it is a corrosive substance that causes rust and oxidation, and therefore it may not be placed close to his neighbor's wall.
"Hasid" - lime. Fresh lime is hot, and also highly burning and corrosive. This is not referring to dry plaster, but to hot lime, whose heat is liable to damage the wall.
"Hasela'im" - rocks. The Bartenura, following the approach of Rashi, explains that these are rocks from which fire emerges, like flint stones, which when struck against each other emit sparks. The Ramban explains that this refers to rocks that contain iron ore, which develop rust that spreads and corrodes the neighbor's wall.
Regarding all of these, it states that one must distance them "mikotlo shel chavero sheloshah tefachim" - three handbreadths from his fellow's wall, which is about thirty centimeters - "vesad basid" - and plaster with lime. Here, the connective letter "vav" (and) must be understood to mean "or": either distance it three handbreadths so the heat does not damage the wall, or coat his fellow's wall with plaster to protect it from the heat emitted by the decomposing material. Although in the previous line, "vesad basid" was understood as an addition, making the wording here somewhat problematic; indeed, there are versions that explicitly read "o sad basid" (or plaster with lime), and this version aligns better with the explanation.
Activities That Undermine a Wall's Foundations:
The next case also deals with a wall above ground, such as the wall of a barn, a shed, or a house. However, here it involves activities that loosen the earth and undermine the foundations of the wall:
"Marchikin et hazeraim" - they distance seeds. Planting close to the wall causes roots to strike into the ground and loosen it, and the earth undermines the foundations of the wall.
"Ve'et hamachreshah" - and the plow. Plowing nearby loosens the ground and shakes it, thereby undermining the foundations of the house and damaging the wall.
"Ve'et mei raglayim" - and urine. When a wall is built of dried clay bricks, contact with urine dissolves the clay. However, if the wall is built of stones without mortar, it does not crumble and no distancing is required at all.
The required distance for all of these is: "min hakotel sheloshah tefachim" - three handbreadths from the wall, which is about thirty centimeters from his fellow's wall.
Distancing the Millstones and the Oven:
The final case deals with activities involving vibration and heat. One who grinds by hand uses two stones placed on top of one another, which the Mishnah calls the rechev and the shechev (we already learned at the end of Tractate Bava Metzia regarding "the rechev and the millstones", and the "millstones" mentioned there are the shechev mentioned here). The surfaces of the stones are very rough, and there is significant friction between them: a person pours the grains between the two stones and turns the upper one, the rechev, and the grains are ground into flour. These stones are heavy, and the vibrations created by turning them shake the ground and undermine the stability of the neighbor's walls, and therefore they must be distanced.
And this is the language of the Mishnah: "umarchik et harechayim sheloshah min hashechev, shehen arba'ah min harechev" - and he distances the millstones three handbreadths from the lower millstone, which is four handbreadths from the upper millstone - a distance of three handbreadths, so the vibrations do not damage the wall. The reason for the two measurements is that the lower stone is slightly wider than the upper one, and the flour gathers on this edge. Thus, the two measurements are actually one: three handbreadths from the lower shechev stone are exactly four handbreadths from the upper rechev stone, which is recessed further back.
Similarly, "ve'et hatanur" - and the oven. The ovens of the Sages were conical in shape - wide at the bottom and narrow at the top, like a small furnace where the heat escapes from the top opening. Furthermore, they would place them on clay bases, as explained in Tractate Keilim, which were also trapezoidal: wide at the bottom and narrow at the top. This base was intended to prevent the ground from cooling and impairing the oven's function, so the fire was set on the clay stand. Since the base sloped inward at an angle, the measurement was taken in two ways: "sheloshah min hakalya" - three handbreadths from the bottom of the base, "shehen arba'ah min hasafah" - which are four handbreadths from the top edge of the base, which is recessed slightly inward. In all these cases, the reasoning is the same: so the heat does not damage the neighbor's wall.
In summary: In this Mishnah we learned four cases of distancing sources of damage: digging a pit, ditch, cave, water canal, or a launderer's pool near a fellow's pit - distancing three handbreadths from the wall and plastering with lime; distancing olive waste, manure, salt, lime, and rocks from a fellow's wall due to the heat and corrosion - three handbreadths or plastering the wall; distancing seeds, a plow, and urine that undermine the foundations of the wall - three handbreadths; and distancing millstones and an oven due to vibration and heat - three from the lower stone which are four from the upper stone, and three from the base which are four from the rim. The foundational principle of them all is one: even when one is acting within his own property, he is commanded to safeguard the peace of his neighbor, in accordance with the way of the Torah, for all its paths are peace.