Praise be to Allaah.
In Islam the mahr (dowry) is one of the rights of the wife, which is hers to take in total and is lawful for her, in contrast to the widespread practice in some countries, where the wife is given no dowry. Evidence that the wife must be given her dowry is found in many places, for example the aayah (interpretation of the meaning): “And give to the women (whom you marry) their mahr (obligatory bridal money given by the husband to his wife at the time of marriage) with a good heart…” [al-Nisaa’ 4:4]
Ibn ‘Abbaas said: “This refers to the mahr (dowry).”
Ibn Katheer, may Allaah have mercy on him, said, summarizing the comments of the mufassireen on this aayah: “The man must definitely pay the dowry to the woman, and he should not resent it.”
Allaah says (interpretation of the meaning): “But if you intend to replace a wife by another and you have given one of them a cantar (of gold, i.e., a great amount) as mahr, take not the least bit of it back; would you take it wrongfully without a right and (with) a manifest sin? And how could you take it (back) when you have gone in unto each other, and they have taken from you a firm and strong covenant?” [al-Nisaa’ 4:20-21]
Ibn Katheer, may Allaah have mercy on him, said: “This means: if any one of you wants to divorce his wife and replace her with another, you should not take anything from what you have already given the first wife, even if it was a huge amount of wealth. The mahr is given in exchange for the right to enjoy marital relations. For this reason Allaah says (interpretation of the meaning): “And how could you take it (back) when you have gone in unto each other…?” The “firm and strong covenant” is the marriage contract.
Anas ibn Maalik, may Allaah be pleased with him, reported that ‘Abd al-Rahmaan ibn ‘Awf came to the Messenger of Allaah (peace and blessings of Allaah be upon him), and there were traces of yellow (perfume) on him. The Messenger of Allaah (peace and blessings of Allaah be upon him) asked him about it, and he told him that he had just married a woman of the Ansaar. The Prophet (peace and blessings of Allaah be upon him) asked him, “How much did you give her?” He said: “Gold equal to the weight of one date stone.” The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Give a waleemah (wedding feast) even if only with one sheep.”(Reported by al-Bukhaari, 4756).
The mahr is the right of the wife, and it is not permitted for her father or anyone else to take it except with her approval. Abu Saalih said: “When a man married off his daughter, he would take her mahr away from her, but Allaah forbade them to do that, and gave women the right to the mahr they received.” (Tafseer Ibn Katheer).
Similarly, if the wife foregoes any part of the mahr, the husband is permitted to take it, as Allaah says (interpretation of the meaning): “… but if they, of their own good pleasure, remit any part of it, take it, and enjoy it without fear of any harm (as Allaah has made it lawful).” [al-Nisaa’ 4:4]
And Allaah knows best.