Does the sale that took place a year ago by mutual consent between two brothers, the price of which has not been fully paid, remain valid and due for payment, or do the buyers have the right to withdraw from the purchase? And would they incur sin if they withdrew from the sale?

If a sales contract has been concluded, fulfilling its conditions, neither party has the right to unilaterally annul it except with the consent of the other party, based on the Almighty’s saying: "O you who have believed, do not consume one another’s wealth unjustly but only [in lawful] business by mutual consent."

The aforementioned sale is binding upon the two brothers, and they are obligated to pay their brother his share, unless he agrees to release them from the contract. The other party is not obligated to respond to a request for annulment, although it is recommended for him to do so. If the brother does not agree to annul the contract, then his full right must be paid to him.