أَن تَبْتَغُواْ بِأَمْوَلِكُمْ That you may seek (to marry) through your wealth: It means that the description of women unlawful for marriage is there to induce you to look for lawful women with the help of your wealth and enter into marriage with them. In Ahkam al-Quran, Abu Bakr al-Jassas writes that this part of the ayah tells us two things.
Firstly, marriage cannot materialize devoid of dower (even if the parties to marriage decide between themselves that the marriage will take place without dower, still, dower will be necessary, details of which are available in books of fiqh). Secondly, it tells us that dower should be something which can be termed as “mal” (inclusive of wealth, property, assets, etc.) According to the Hanafiyyah, mahr should not be less than ten dirhams. One dirham is equivalent to 3 ½ x 17 grains Troy of silver.
مُّحْصِنِينَ غَيْرَ مُسَـفِحِينَ desiring chastity not lust: It means that one should seek lawful women with the help of one’s assets and it should be clearly understood that the seeking of women is to safeguard modesty and chastity, which is the crucial purpose of a marriage. And it is through marriage alone that the desired objective has to be achieved and certainly not through spending to find women for zina. This tells us that, no doubt the fornicators too spend out of their assets, but that spending is patently unlawful, and benefiting from a woman who has been procured by such spending is never lawful. The addition of غَيْرَ مُسَـفِحِينَ not for lust here serves two purposes. As obvious, it forbids zina while it also points out that the purpose of zina is nothing but to run after lust and to waste one’s semen for unlawful enjoyment because it is not aimed at the seeking of children and the preservation of the human race. Muslims must stay chaste investing their strength where it is due in the best interest of human procreation, the method of which is to have a wife in marriage, or a bondwoman – in case one comes to have one.
So for whatever you benefit from them, given them their bridal due as an obligation: Benefiting in this ayah refers to coition and it means that the payment of full dower is due on the husband only when he had benefited from her company by having sex with her. If, after the initial marriage contract the wife has not come to live with the husband who thus does not get the opportunity to benefit from her company, and he divorces her before having that opportunity, the payment of mahr due against him becomes half. Special attention has been drawn in this ayah to the situation when one this benefit has been received from some woman, the payment of her mahr becomes obligatory on all counts. Any shortcoming in doing so is against the letter and spirit of Muslim law. Moreover, the universal human sense of honor dictates that consequent to the purpose of marriage having been achieves, there should be no failing or delaying in giving the wife her due however, the Shariah gives the woman the additional right that she can, if the mahr is prompt (muajjal) refuse to go to her husband until the payment of the mahr has been made to her.
(Taken from Maaruf-ul-Qur’an by Mufti Muhammad Shafi Usmani)