Deuteronomy 19:14

You shall not remove the boundary mark of your neighbours which the predecessors did set for the limit in your possession of inheritance in the land which the Lord your God giveth you to inherit.

The meaning of the word remove is known; it has a meaning close to “destroy”. Compare, “remove not the ancient landmark” [Proverbs 22: 28].

primogenitors those who parceled out the land. This passage is juxtaposed to the previous one because land encroachment leads to arguments, to blows, and to murder. Accordingly, Scripture says later on, “a life for a life, an eye for an eye, a tooth for a tooth…” [: 21].

THOU SHALT NOT REMOVE THY NEIGHBOR’S LANDMARK. This is a warning against changing the boundaries of the division by which the princes apportioned the Land to the tribes or to any individual among them. Therefore he stated, which they of old time have set, these being Eleazar the priest, and Joshua the son of Nun, and the princes of the tribes, and therefore he mentioned in thine inheritance which thou shalt inherit etc. And the reason for this commandment is that no one should contemplate to say, “My portion which they gave me is not as valuable as the portion of my friend, because the dividers erred,” or he may feel suspicious of the lots, thus he will not consider it [his removal of the boundary marker] to be robbery at all. Therefore he commanded here that no one should controvert that division, and he may not make any change in the boundaries, either secretly or openly. Now this is an explanatory commandment, deriving from what He commanded, According to the lot shall their inheritance be divided between the more and the fewer, and He further stated, These are the names of the men that shall take possession of the Land for you., 34:17. And in the opinion of our Rabbis 188. that this verse is an admonition, teaching us that one who encroaches on his neighbor’s land in the Land of Israel transgresses two commandments, (Leviticus 19:13), and the verse before us. Outside the Land of Israel he transgresses only the commandment against committing robbery. See “The Commandments,” Vol. II, pp. 234-235. the meaning of the expression which they of old time have set means that one is not to secretly change an old boundary and say “It was always here.” Scripture admonishes [concerning an old boundary] because it speaks of what usually happens, for a new boundary is recognized and known and no one changes it. Our Rabbis themselves have mentioned [the first interpretation, for thus they said in the Sifre]: 188. “Whence do we know that one who uproots the boundaries of the tribes transgresses a negative commandment? Because Scripture states, Thou shalt not remove thy neighbor’s landmark, [which they of old time have set].” This is truly the plain meaning of Scripture.

לא תסיג, the word is similar in meaning to Isaiah 42,17 נסוגו אחור, “they retreat backwards.” Our verse describes someone who adjusts his neighbour’s boundary backwards in order to increase the size of his own land.