Leviticus 25:39-41, 44

‘If a countryman of yours becomes so poor with regard to you that he sells himself to you, you shall not subject him to a slave’s service. He shall be with you as a hired man, as if he were a sojourner; he shall serve with you until the year of jubilee. He shall then go out from you, he and his sons with him, and shall go back to his family, that he may return to the property of his forefathers.

As for your male and female slaves whom you may have—you may acquire male and female slaves from the pagan nations that are around you.