One of the preferences in the matter of conflicting in time between two obligations is time primacy. An instance for this is the case of a person's religious vow to make a pilgrimage to Karbala in Arafa, before he can afford to go to Hajj pilgrimage, and after the vow, he becomes capable of doing so. Now, the question arises here as to whether he should make a pilgrimage to Karbala in Arafa or have a pilgrimage to Mecca and fulfill the Hajj obligation. Some jurisprudents believe in vow primacy and rely on some reasons like the inability to fulfill Hajj in the case of vow, institutional agreement, the primacy of vow over Hajj, and Halabi's narration (Sahiha). Most of the jurisprudents have judged on the Hajj primacy, although they have proposed different views; some of them believe in the nullification of vow, others believe that the subject is irrelevant, and others have judged on the primacy of Hajj based on the primacy of conditional obligation with innate rational ability over the conditional obligation with religious ability. Analyzing the two groups’ reasons, this article approved the primacy of Hajj based on three reasons: (vow’ s accompaniment with God disobedience, necessity of permission for the vow, absence of religious permission for vow, and some hadiths about Hajj). The neglected point is that the "time primacy" is valid when there is no other characteristic, which leads to the preference of the later. Here, given the acceptance of the conflict and placing Hajj in the later position, due to other characteristics that makes Hajj more important, it should have priority over vow, because merely the time priority could not strengthen incumbency.