The necessity of accomplishing the contract has been expressed in the form of the principle of irrevocability, the irrevocability of fulfilling the contract, fulfilling the covenant, holiness and compulsory of contracts, irrevocability and compulsory of contract. The purpose of all these principles is summarized in the contract and becomes a binding force as soon as it is created, to which the parties participating are bound by its provisions. In jurisprudence and Iranian law, the pacta sunt servanda is interpreted as the principle of the irrevocability of contracts. the pacta sunt servanda has been accepted in jurisprudence and Iranian law. The principle of irrevocability is different from that of the pacta sunt servanda. From 219 of the Civil Code, some have inferred the principle of irrevocability in the position of doubt in the revocability and irrevocability of contracts, and others have inferred the pacta sunt servanda of absolute contracts, both revocable and irrevocable. This article tries to identify the pacta sunt servanda in Iranian law, provisions, concepts, and sources and explain its differences with the principle of irrevocability and similar principles in Iranian law, jurisprudence, and foreign law