Albert Barnes Commentary Leviticus 25:44-46

"And as for thy bondmen, and thy bondmaids, whom thou shalt have; of the nations that are round about you, of them shall ye buy bondmen and bondmaids. Moreover of the children of the strangers that sojourn among you, of them shall ye buy, and of their families that are with you, which they have begotten in your land: and they shall be your possession. And ye shall make them an inheritance for your children after you, to hold for a possession; of them shall ye take your bondmen for ever: but over your brethren the children of Israel ye shall not rule, one over another, with rigor." — Leviticus 25:44-46 (ASV)

Property in foreign slaves is distinctly permitted here. It was a patriarchal custom (Genesis 17:12). Such slaves might be captives taken in war (Numbers 31:6 and following; Deuteronomy 20:14), those consigned to slavery for their crimes, or those purchased from foreign slave-dealers.

The price of a slave is supposed to have varied from thirty to fifty shekels. See the note on Leviticus 27:3-4; the note on Exodus 21:32; the note on Zechariah 11:12-13; and the note on Matthew 26:15.

It was the object of Moses not to abolish slavery at once, but to discourage and mitigate it. The Law would not allow it to be forgotten that the slave was a man, and protected him in every way that was possible at the time against the injustice or cruelty of his master. See the notes on Exodus 21.

(Leviticus 25:46)

Your bondmen forever—that is, they were not necessarily to be released in the sabbatical year nor in the Jubilee.