Buyers of a house contended that the seller has no right to terminate the sale agreement for their failure to pay the main installment on time and despite the provisions of the agreement that allow him to do so. This is because from the behavior of the parties, after the signing of the agreement, and in particular from the seller's waiver of delays in making previous payments, it can be inferred that the parties agreed to change the provisions of the agreement.
The Court rejected the contention of amendment of contract by behavior. While the behavior of the parties after the conclusion of the contract constitutes an important interpretive tool, which serves to testify to the intention of the parties at the time of the signing of contract and the manner in which they understood the contract, this interpretive tool is essentially concerned with determining the interpretation to be given to the intent of the parties at the time of entering into the agreement and their understanding of the nature of the agreement. However, in a case where it is contended that the behavior of the parties has the effect of changing a written contract, a heavy burden is placed on the person making that claim. Here, waiver of a claim resulting from a late payment of 8% of the consideration, which is not a material breach, cannot constitute evidence of granting a blanket waiver of not making payments on time, and certainly not when it comes to the payment of approximately 72% of the consideration, which was explicitly defined in the agreement as a "material breach".