Purchaser's Unauthorized Transfer Voids Right to Specific Performance Under Promise to Sell

A party who had purchased a building under a promise to sell, and subsequently transferred their rights to a third party without the seller's consent, as required by the promise to sell, sought to enforce specific performance after the seller later refused to sell to the initial purchaser, arguing the prohibition on transfer was merely a condition subsequent. The court held that the stipulation in the promise to sell prohibiting the transfer of the purchaser's rights without the seller's prior written agreement was a condition precedent to the final contract, and since the initial purchaser failed to fulfill this condition by transferring the rights without authorization, the seller was justified in refusing to proceed with the final sale, leading to the cassation of the lower court's decision ordering specific performance.