An-Nisaa 4:24

Also [prohibited are] married women except for female slaves you may own. This is Allah’s commandment to you. All women other than these are lawful for you to marry with your wealth in a legal marriage, not adultery. When you consummate your marriage with them, give them their due dowries[17]. There is no sin on you to mutually agree after the [initial] agreement. And Allah is All-Knowing, All-Wise.

[17] The mahr, a specified gift to the bride required of the man upon marriage.

And [also prohibited to you are all] married women except those your right hands possess.[177] [This is] the decree of Allāh upon you. And lawful to you are [all others] beyond these, [provided] that you seek them [in marriage] with [gifts from] your property, desiring chastity, not unlawful sexual intercourse. So for whatever you enjoy [of marriage] from them, give them their due compensation[178] as an obligation. And there is no blame upon you for what you mutually agree to beyond the obligation. Indeed, Allāh is ever Knowing and Wise.

[177] i.e., slaves or war captives who had polytheist husbands.
[178] The mahr, a specified gift to the bride required of the man upon marriage.

24. Also (forbidden are) women already married, except those (slaves) whom your right hands possess. Thus has Allâh ordained for you. All others are lawful, provided you seek (them in marriage) with Mahr (bridal-money given by the husband to his wife at the time of marriage) from your property, desiring chastity, not committing illegal sexual intercourse, so with those of whom you have enjoyed sexual relations, give them their Mahr as prescribed; but if after a Mahr is prescribed, you agree mutually (to give more), there is no sin on you. Surely, Allâh is Ever All-Knowing, All-Wise.

And all married women (are forbidden unto you) save those (captives) whom your right hands possess. It is a decree of Allah for you. Lawful unto you are all beyond those mentioned, so that ye seek them with your wealth in honest wedlock, not debauchery. And those of whom ye seek content (by marrying them), give unto them their portions as a duty. And there is no sin for you in what ye do by mutual agreement after the duty (hath been done). Lo! Allah is ever Knower, Wise.