The Women - 4:25 Those of you who cannot afford to marry free women, let them marry those to whom your believing oaths/agreements entitle you. Allah is the Best Knower of your faith. You are equal to each other. Marry them with the permission of their owners and pay them their mahr accordingly. Let them live chaste lives, not committing adultery and not taking secret friends. If they commit adultery after they have gained their freedom through marriage, they should be punished with half the punishment given to free women. This is for those of you who fear sin. It is better for you if you are patient. Allah is Forgiving, Merciful.
Related:
The Women/4:32 Do not covet what Allah has bestowed on each of you. For men a share of what they earn and for women a share of what they earn. Ask Allah to bestow His grace upon you. Allah is All-Knowing.

The Family Of Imran/3:195 "Their Lord answered them: "I will not leave unrewarded any of you who works, whether male or female; you are all equal. Those who emigrated, those who were expelled from their homes, those who were tortured and insulted in My way, those who fought and were killed... I will cover their evil deeds and place them in gardens with rivers flowing in them as a reward from Allah. The best reward is with Allah."