In Quran (4:22-24) the list of relations prohibited for marriage begins with the step mother and ends with women who are married to someone. In between these two, the prohibited women mentioned are based on the three bases of relationship: Lineage, Fosterage and Marriage.
As far as the relationships prohibited for marriage on the basis of marriage itself are concerned, the daughter-in-law is prohibited for the father, and the mother-in-law, the wife’s daughter, the wife’s sister and both nieces of the wife, the maternal and paternal aunts of the wife are all prohibited for the husband. However, since these relationships are formed through the husband and the wife, a degree of weakness is found in them. Owing to this reason, the Quran has imposed the following three conditions on the prohibition of these relationships:
Firstly, only the daughter of that wife is prohibited with whom one has had conjugal contact.
Secondly, only the daughter-in-law of a real son is prohibited.
Thirdly, the sister of a wife, her maternal and paternal aunts and her two nieces are only prohibited if the wife is in wedlock with the husband.
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Discussion 29875