The aim of the present study is to examine the jurisprudential and legal condition of returning an endowment to the donor’s property. The main challenge in discussing the condition of returning in an endowment is the conflict between the fundamental principles of endowment and the possibility of including conditions in contracts. From a jurisprudential and legal perspective, endowment is by its very nature a necessary and permanent contract whose purpose is to permanently confine the object and obtain its benefit for good purposes. The prohibition of the donor’s return after the endowment is realized, which guarantees the sustainability and achievement of the endowment’s objectives, is considered one of its main pillars. However, the inclusion of a condition of return that allows the donor or a third party to terminate the endowment and return the endowment object to its original ownership challenges this necessity and prohibition of return. Most jurists and lawyers believe that such a condition is in conflict with the requirements of the essence of the endowment contract, because it removes the endowment from the state of permanent possession or confinement and turns it into a permissible contract, which contradicts the long-term goals and the sustainable nature of the endowment and makes it invalid; this view faces serious challenges due to the destabilizing consequences for the endowment institution. The research peresent, using an analytical-descriptive method, has concluded that the condition of the return of the endowment to the donor’s property is in fundamental conflict with the necessary and eternal nature of the endowment and the principle of “prohibition of return from the endowment”. The dominant jurisprudential and legal view in Iran considers such a condition invalid due to its contradiction with the requirements of the essence of the endowment contract and the need to maintain the stability and stability of this benevolent institution and emphasizes it in order to prevent instability in the pillars of the endowment and the loss of its lofty goals.