Guarantee of something that is not obligatory means a commitment to something that does not exist at the time of guarantee. There is a difference of opinion among Islamic jurists regarding its validity. Most Shiite jurists consider this type of guarantee to be invalid. The later jurists of the Shafi'i school of thought also agree with the famous Imami theory, but the Hanafi, Hanbali, Maliki, and early Shafi'i schools of thought have issued fatwas opposing the Imami opinion. Those who believe in its invalidity have mainly relied on two reasons, one is that the guarantee contract is subordinate to religion, and the other is the consensus of jurists. In this study, we have come to the conclusion that the issue of guaranteeing what is not required is valid and there is no evidence to invalidate it. Its correct analysis, which does not involve any of the problems raised on this issue, is as follows: Guaranteeing what is not required is considered a matter of credit, and therefore its validity and invalidity depend on whether such a guarantee is, according to the rational people, an effect and is outside of the literal sense or not. In cases where the religion does not exist in an actual way or not in a contingent way, the guarantor guarantees something that exists in its own container; such as Amr saying that when the religion comes to Zayd's attention, I will be its guarantor. Here, the guarantor's commitment to the credit is a commitment that the subject will be committed to in the future. Such a matter is permissible in the world of legislation and credit and will not cause any problems.