Summery:- The theory of obligations in general and contracts in particular is the backbone of any legal system, and the principle of dominion of will dominates over the rules of contracts in modern laws, both at the level of its formation or at the level of its effects, which is what he called the rule of "the law of contracting parties". This was referred to in Article 147 of the Egyptian Civil Code, as it states: “The contract is the law of the contracting parties. In order to achieve this, if the contract is valid and arranged for its effects, it is the responsibility of its parties to implement it in good faith and what is required by honesty.