The Halacha of "Bar Masra" states that when a person sells a house or tract of land, he must grant the owner of the neighboring property the right of first refusal. If the seller sold the property to somebody else without first offering it to the neighbor, the neighbor can go to Bet Din (the Rabbinical Court) to have the sale annulled.
Generally, the neighbor can exercise his right of first refusal only immediately upon hearing of the sale; if he does not go to Bet Din immediately upon his hearing of the sale, he cannot go to them later to demand the sale's annulment. The exception to this rule, however, as the Rama (Rabbi Moshe Isserles, Poland, 1525-1572) rules in his glosses to the Hoshen Mishpat section of the Shulhan Aruch (175:32), is when the neighbor was unaware of the Halacha of "Bar Masra" when the sale occurred. If he did not immediately exercise his right of first refusal due to ignorance of this Halacha, when he learns this Halacha he may then exercise his right. Even if he hears of this law only several months or years later, he may approach Bet Din and have them annul the sale and allow him to purchase the adjacent property.
Does a business partner enjoy the right of first of refusal? Namely, if a partner in a business decides to sell his share of the company, must he first offer the share to the other partner, or can he sell it to whomever he wishes?
The Rama (ibid. 175:53) rules that the law of "Bar Masra" applies only to real estate, and therefore a business partner is not required to first offer his share to the other partner. If, however, he sells his share to somebody with whom the other partner feels incompatible, the other partner can appeal to Bet Din to annul the sale. Since he feels incapable of running the business with the new partner, he has the right to demand the revocation of the sale.
Summary: When a person sells a piece of real estate, the owner of the neighboring property has the right of first of refusal which he must exercise immediately. If the land was sold to somebody else and the neighbor did not immediately demand its revocation, he forfeits his right of first refusal, unless he had been unaware of this Halacha at the time of the sale. One who sells his share in a business is not required to first offer the share to his partner; however, if the partner feels incapable of working with the buyer of the other share, he can appeal to Bet Din to revoke the sale.
See the book- "Pure Money" by Dayan Cohen, pages 176-178.
