4/An-Nisa-24: And to marry all married women (are forbidden to you) except the concubines in your possession (female prisoners of war). (These are) Allah’s ordinances (obligations) to you. And lawful for you are (all women) besides those, provided that you seek (them) the chaste ones with your property (offering Mahr) taking (them) in marriage not committing fornication. Then as to those whom you would like to be with, give them their Mahr as prescribed. But after this obligation, if you agree mutually, then there is no sin on you. Surely, Allah is All-Knowing, All-Wise.
4/An-Nisa-25: And whoever of you is not able to afford to marry from the free, believing women, then he may marry from among your believing young concubines in your possession and Allah knows best your faith; you are (sprung) the one from the other. So marry them with the permission of their masters and give them their Mahr on a reasonable basis within their customs. As they should be chaste, not adulterous nor receiving secret boy-friends, when they are taking them in marriage. If they are guilty of adultery, then they shall suffer half (the punishment) which is upon free women. This (permission to marry a concubine) is for him among you who fears to commit adultery. And to have patience would be better for you. And Allah is Oft-Forgiving, Most Merciful.
4/An-Nisa-26: Allah wishes to make clear to you and guide you to the laws of those before you and accept your repentance, and Allah is All-Knowing, All-Wise (the Owner of Judgment and Wisdom).