Where parol contemporaneous agreement the moving cause of written contract

In the case at bench, the fact which private respondents seeks to establish by parol evidence consists of the agreement or representation made by the NAC that induced Inez Ouano to execute the deed of sale; that the vendors and their heirs are given the right of repurchase should the government no longer need the property. Where a parol contemporaneous agreement was the moving cause of the written contract, or where the parol agreement forms part of the consideration of the written contract, and it appears that the written contract was executed on the faith of the parol contract or representation, such evidence is admissible. It is recognized that proof is admissible of any collateral parol agreement that is not inconsistent with the terms of the written contract though it may relate to the same subject matter. The rule excluding parol evidence to vary or contradict a writing does not extend so far as to preclude the admission of existing evidence to show prior or contemporaneous collateral parol agreements between the parties but such evidence may be received, regardless of whether or not the written agreement contains any reference to such collateral agreement, and whether the action is at law or in equity. [G.R. No. 121506. October 30, 1996]