In all religions and legal systems, marriage has been always protected by the government and legislature due to its unique effects on the health and the survival of society. Sexual reproduction, on which the survival of nations depends, is indebted to sexual enjoyment. Therefore, the obligations of the spouses for having safe sexual relationship, the conditions governing such a relationship (including the conditions permitting the prohibition or limitation of intercourse), and the study of their legal status are of great importance.A precise review of the scholars and authors, who studied this issue, indicates that there is a deep difference among the Islamist Jurisprudents and jurists. It seems that the main cause of this difference is because there is no consensus on the legal definition and nature of marriage, and distinguishing its requirements of substance from other requirements. Some scholars argue that sexual enjoyment and coupling is the purpose of marriage contract, and others believe in matrimony as the objective of marriage. There are also other scholars, who argue cooperation and participation in life are the purposes of marriage.For this purpose, we firstly try to introduce the nature of marriage contract, and answer what the requirements of the substance of marriage are. Thereafter, we discuss the conditions governing the sexual relation between spouses.