Negative Mitzvah 85– This is a negative commandment: do not encroach beyond a neighbor’s boundary, specifically in the Land of Israel.
Hafetz Hayim – As Scripture says: “You shall not move your neighbor’s landmark … in your inheritance which you shall inherit” (Deut. 19:14). which means taking some of his land. If a person entered his neighbor’s domain even by the breadth of a finger, even outside the Land of Israel – if it was by main force, he is thus a robber; if it was by stealth, he is a thief.
This applies everywhere and always, for both men and women.
When we purchase a piece of property, no matter if we are financing the purchase or paying cash, a survey of the property is always required. It only makes sense that when we purchase property, we know the exact dimensions of what we are buying and the exact location of the property boundaries (where my property ends and someone else’s property begins).
In the days before modern surveying, landmark stones were put in place at the corner of private property and sales contracts were written concerning the land between these marker stones. Once these stones were in place, it was forbidden to move them. After all, as we see in the Torah and in the Mitzvah above, moving the stone was tantamount to stealing a neighbor’s land. If you were to purchase an adjoining field, you might, together with your neighbor, move the stones to the new property line, but if you do it by stealth, you are a common thief. If you take the land at gunpoint (or sword point) you have committed an act of armed robbery. I should also note that in Deuteronomy 27:17, there is a special public curse recited by all the people assembled between the mountains of Ebal and Gerizim directed at anyone who would move his neighbor’s landmark.
Clearly landmarks were easy to move and the temptation to move them and gain a bit more land for free was strong. The system of property markers required a bit of personal honesty among neighbors to prevent boundary disputes that even with our modern surveys, we find all too often still can sour the relationship between neighbors. Since these landmark stones could be moved and the other party none the wiser, this was considered a seriously nefarious criminal act and ancient society had only its most severe disdain to enforce what was basically an honor system.