The general rule is that the parties to the contract are subject to the principle of sovereignty of the will and its independence. However, recently in Scandinavian countries, unwritten principles such as the duty of loyalty have also been cited, which mainly means that; "The parties must consider each other's interests and expectations in a reasonable and conventional manner, without unreasonably neglecting their own interests", which is defined as limiting the contractual freedom of the parties, and the violation of this duty has the same effects and consequences as the violation of the contract. Indeed, one of the common principles in the field of contract law in the Nordic countries is the commitment to Loyalty, which is defined as a requirement to consider or even take care of the interests of the other party. Reflecting on the background of this obligation tells us that due to its compatibility with conscience and human nature, from the distant past, the contracting parties followed it not according to the law, but according to ethics and fairness in their transactions. In jurisprudence, the results and The duties of this duty can be inferred from the topics of misrepresentation, gash, najsh and Receiving caravans. From the point of view of jurisprudence, the contents of commitment to loyalty can be deduced from the collection of Quranic verses and hadiths, and its traces are evident in concepts such as Misrepresentation, percentage or murabaha, najsh, rule of prohibition of detriment and Receiving caravans and In Iranian law, it can be based on Article 279 of the Civil Code or the Lesion Optionon mentioned in Articles 416 and later of the said law and the defect of Article 422 and later of the same law.