Quran 4:24 — Women (Al-Nesa')

Also prohibited are the women who are already married, unless they flee their disbelieving husbands who are at war with you.* These are GOD's commandments to you. All other categories are permitted for you in marriage, so long as you pay them their due dowries. You shall maintain your morality, by not committing adultery. Thus, whoever you like among them, you shall pay them the dowry decreed for them. You commit no error by mutually agreeing to any adjustments to the dowry. GOD is Omniscient, Most Wise.

[4:23] Prohibited for you (in marriage) are your mothers, your daughters, your sisters, the sisters of your fathers, the sisters of your mothers, the daughters of your brother, the daughters of your sister, your nursing mothers, the girls who nursed from the same woman as you, the mothers of your wives, the daughters of your wives with whom you have consummated the marriage—if the marriage has not been consummated, you may marry the daughter. Also prohibited for you are the women who were married to your genetic sons. Also, you shall not be married to two sisters at the same time—but do not break up existing marriages. GOD is Forgiver, Most Merciful.

[4:25] Those among you who cannot afford to marry free believing women, may marry believing slave women. GOD knows best about your belief, and you are equal to one another, as far as belief is concerned. You shall obtain permission from their guardians before you marry them, and pay them their due dowry equitably. They shall maintain moral behavior, by not committing adultery, or having secret lovers. Once they are freed through marriage, if they commit adultery, their punishment shall be half of that for the free women.* Marrying a slave shall be a last resort for those unable to wait. To be patient is better for you. GOD is Forgiver, Most Merciful.