10. The Principle of Marital Relations
The Quran states: “You are forbidden to take as wives your mothers, daughters, sisters, paternal and maternal aunts, your brothers’ daughters and your sisters’ daughters, your foster mothers and foster sisters, your wives’ mothers and stepdaughters in your protection and the daughters of your wives with whom you have consummated your marriage; but if you have not consummated your marriage then you will not be blamed [if you marry their daughters]. You are also forbidden to marry the spouses of your sons or two sisters together, except what has already passed. Surely, God is ever-forgiving and merciful.” (Quran, 4:23)
Under Islamic law, marriage is permitted with some relatives and prohibited with others. Women with whom marriage is prohibited fall into several categories. Seven categories are prohibited on account of blood relationship: one’s mother, daughter, sister, paternal aunt, maternal aunt, brother’s daughter, and sister’s daughter. Marriage to any woman belonging to these categories is unlawful.
The term “mother” includes one’s grandmothers and all female ascendants, however remote. Similarly, the term “sister” includes all three types of sisters: a full sister, who shares both parents; a paternal half-sister, who shares the same father but has a different mother; and a maternal half-sister, who shares the same mother but has a different father.
The category of “paternal aunt” includes the full and half-sisters of one’s father, paternal grandfather, and all male ascendants. The category of “maternal aunt” includes the full and half-sisters of one’s mother, maternal grandmother, and all female ascendants.
The category of “brother’s daughter” includes the daughters and all female descendants of one’s full brother, paternal half-brother, and maternal half-brother. Likewise, the category of “sister’s daughter” includes the daughters and all female descendants of one’s full sister, paternal half-sister, and maternal half-sister. Marriage to any of these women is prohibited.
Certain relationships are also prohibited on account of fosterage through breastfeeding. The two principal relationships mentioned are those of foster mother and foster sister. However, all seven categories prohibited by blood relationship are likewise prohibited through fosterage. Thus, marriage is also prohibited with one’s foster daughter, foster paternal aunt, foster maternal aunt, foster brother’s daughter, and foster sister’s daughter.
Marriage may also be prohibited on account of affinity, that is, relationships created through marriage. This prohibition is of two kinds.
The first is permanent prohibition. A man may never marry his wife’s mother or the daughter of a wife with whom he has consummated the marriage. However, if he divorces a woman before consummation, he may marry her daughter. He is also permanently prohibited from marrying the wives of his sons, including the wives of his grandsons and all male descendants.
The second is temporary prohibition. In such cases, marriage remains prohibited only for as long as the woman remains married to him. If the marriage ends through divorce or the wife’s death, marriage with certain of her relatives becomes permissible. For example, a man may not marry his wife’s sister while he is still married to his wife, but he may do so after the marriage has ended. The same rule applies to his wife’s paternal aunt, maternal aunt, brother’s daughter, and sister’s daughter. (Tafsir Usmani)
