Negative commandment · Lo Ta’aseh #246 of 613
Not to alter land boundaries
שלא להסיג גבול
The verse · Devarim 19:14
לֹא תַסִּיג גְּבוּל רֵעֲךָ אֲשֶׁר גָּבְלוּ רִאשֹׁנִים בְּנַחֲלָתְךָ אֲשֶׁר תִּנְחַל בָּאָרֶץ אֲשֶׁר ה׳ אֱלֹהֶיךָ נֹתֵן לְךָ לְרִשְׁתָּהּ
“Thou shalt not remove thy neighbour’s landmark, which they of old time have set in thy inheritance, which thou shalt inherit in the land that the Lord thy God gives thee to possess it.”
The Rambam’s words
Not to alter land boundaries, as [Deuteronomy 19:14] states: "Do not remove your neighbor's landmark."
שלא להסיג גבול, שנאמר "לא תסיג גבול ריעך" (דברים יט,יד).
Why · Sefer HaChinuch #522
To not remove a landmark
“The root of the commandment about every matter of theft is well-known — as it is something about which the intellect testifies, and it is beneficial for all.”
Who & when
“And it is practiced in every place and at all times by males and females.”
Where in the Mishneh Torah
Hilchot Theft הלכות גניבה