Many natural desires make themselves felt in human beings—sexuality between man and woman being one of these. Islamic law, which fixes a limitation for all human emotions, has determined the limits for sexual relationships also. According to this divine dictate, only that sexual alliance between man and woman is valid which is established through a standard solemn social agreement in the form of marriage. It requires, moreover, that along with the satisfaction of natural desire, an environment of chastity must also prevail in the family life. For this purpose certain close relations have been declared prohibited to keep them beyond and above sexual desires.