In some of the legal texts about the principles of legitimation, “stipulation of a contract” is a contract which does not make an unlawful thing lawful or does not prohibit a lawful thing. Different views have been proposed by the jurists about the meaning of “the condition of prohibition of lawful thing”. Becouse of some intricacies in this regard, it is difficult to provide a clear interpretation of the condition of prohibition of lawful thing. The present article tries to provide a proper meaning of prohibition of lawful with the language of legal proofs. This has been done through consideration of the Quranic root of this term, explanation of the origin of this term within the Quranic verses, and paying attention to the traditions related to the prohibition of lawful while making a comparison with the Quranic verses, as well as making a comparison between them and evidences related to the condition against the Book and Sunnah. Next, it tries to evaluate and criticize the important views of the jurists in this regard. Accordingly, the condition “against the Book and Sunnah” and the condition of “making an unlawful thing lawful and prohibition of a lawful thing” are consistent with each other and cover the permissible things too. In fact, the condition of giving up every permissible act which is characterized as lawful before composing the contract and its stipulation, is an example of a condition of making a lawful thing unlawful, specifically about making benefit of the blessings and lawful desires