Hawkins v. United States

Yerbal agreements between the parties to a .written contract, made before or at the time of the execution of the contract, are in general inadmissible to vary its terms or to affect its construction, the rule being that all such verbal agreements are to be considered as merged in the written instrument. But oral agreements subsequently made, on a new and valuable consideration, and before the breach of the contract, in cases not falling within the Statute of Frauds, stand upon a different footing; as such agreements may, if not within the Statute of Frauds, have the- effect to enlarge the…