The Torah commands in Parashat Shoftim (Debarim 19:14), “Lo Tasig Gebul Re’acha…Be’nahalatecha Asher Tinhal” – “Do not move your fellow’s border…in your portion which you will inherit…” This verse establishes a Biblical prohibition against encroaching on somebody’s property, such as by moving the boundary onto his land, or performing an act displaying ownership (such as agricultural work) on his property, in the Land of Israel. As the Sefer Ha’hinuch explains, the general prohibition of theft forbids encroaching on somebody’s property anywhere, even outside the Land of Israel. (If one moves the border in broad daylight, openly, then he violates the prohibition of “Gezela,” and if he does so clandestinely, then he transgresses the command of “Geneba.”) If somebody does this in Eretz Yisrael, then he transgresses the prohibition of theft as well as the additional prohibition of “Lo Tasig.”
The Sefer Ha’hinuch writes that encroaching even a “Melo Esba” – a finger’s width – on somebody’s property is forbidden. Therefore, people who build homes must exercise extreme care and ensure not to extend beyond the boundary of their property into a neighboring property. Even if the neighbor is unaware of the encroachment, it violates a Biblical command.
The Sefer Ha’hinuch writes that there is no need to explain the reason behind this prohibition, as it is obvious that a functioning, civilized society cannot allow people to seize their neighbors’ property.
This prohibition applies in all times, and is binding upon both men and women. One who extends onto somebody else’s property violates this prohibition but is not liable to Malkut, as this command falls under the category of “Lav Ha’nitan Le’tashlumin” – a violation that can be corrected through payment. One who unlawfully seizes someone’s property must return it – or leave the property – and thereby rectify the wrongdoing, and Malkut are not administered for violations which can be rectified.
The prohibition of “Hasagat Gebul” (encroaching on a person’s property) includes also a different type of encroachment – going into the same business as somebody, thereby ruining his livelihood. When a person wishes to start a business that will compete with an already existing business, he must seek Halachic guidance to determine whether or not this is permissible. While Halacha certainly allows competition in the marketplace, in some circumstances opening a competing enterprise will be forbidden on the grounds of “Hasagat Gebul.” This prohibition applies both in Eretz Yisrael and outside the land.
A famous example of this prohibition is a story involving the Maharam Padua (Rav Meir Katzenellenbogen, Germany-Italy, d. 1565), who, together with a non-Jewish partner, invested a great deal of money into printing of a new edition of the Rambam’s Mishneh Torah. A rival – a wealthy businessman who also owned a printing press – became jealous, and so he printed his own version of the Mishneh Torah, and proceeded to sell it for a far lower price, which the Maharam Padua could not afford to charge. The Maharam Padua lost his enormous investment. He wrote a letter to the Rama (Rav Moshe Isserles, Cracow, 1530- 1572), asking whether the competitor was allowed to do what he did. The Rama responded that the competitor’s actions were forbidden, as they clearly violated accepted business practices, and were undertaken for the purpose of putting the first enterprise out of business. Accordingly, the Rama issued a ban on the competitor’s edition of the Rambam, and the people purchased the Maharam Padua’s edition, rescuing him from financial ruin.
People must be aware that whereas competition in the marketplace is, in and of itself, legitimate, some practices that harm a preexisting enterprise are forbidden, and a competent Halachic authority must be consulted for guidance.