An-Nisa 4:25

Waman lam yastatiAA minkum tawlanan yankiha almuhsanati almu/minatifamin ma malakat aymanukum min fatayatikumualmu/minati wallahu aAAlamu bi-eemanikumbaAAdukum min baAAdin fankihoohunnabi-ithni ahlihinna waatoohunna ojoorahunna bilmaAAroofimuhsanatin ghayra masafihatin walamuttakhithati akhdanin fa-itha ohsinnafa-in atayna bifahishatin faAAalayhinna nisfu maAAala almuhsanati mina alAAathabi thalikaliman khashiya alAAanata minkum waan tasbiroo khayrunlakum wallahu ghafoorun raheem

And whoever among you cannot [find] the means to marry free, believing women, then [he may marry] from those whom your right hands possess of believing slave girls. And Allāh is most knowing about your faith. You [believers] are of one another. So marry them with the permission of their people and give them their due compensation [i.e., mahr] according to what is acceptable. [They should be] chaste, neither [of] those who commit unlawful intercourse randomly nor those who take [secret] lovers. But once they are sheltered in marriage, if they should commit adultery, then for them is half the punishment for free [unmarried] women. This [allowance] is for him among you who fears affliction [i.e., sin], but to be patient is better for you. And Allāh is Forgiving and Merciful.

If one cannot afford to marry the free Muslim women, then (he may marry) the one you people own of your Muslim girls. Allah knows best about your faith. You are similar to each other.So, marry them with the permission of their masters, and give them their dues, as recognized, they being bound in marriage, not going for lust, nor having paramours. So, once they have been bound in marriage, then, if they commit a shameful act, they shall be liable to half of the punishment prescribed for the free women. That is for those of you who apprehend to indulge in sin. But that you be patient is better for you. Allah is Most-Forgiving, Very-Merciful.