John Calvin Commentary Leviticus 25:42

"For they are my servants, whom I brought forth out of the land of Egypt: they shall not be sold as bondmen." — Leviticus 25:42 (ASV)

For they are my servants. God here declares that His own right is invaded when those, whom He claims as His property, are taken into subjection by another; for He says that He acquired the people as His own when He redeemed them from Egypt. From this He infers that His right is violated if anyone should usurp perpetual dominion over a Hebrew.

If anyone objects that this applies equally when they only serve for a time, I reply that although God might have justly asserted His sole ownership, He was satisfied with this symbol of it. Therefore, He permitted by indulgence that they should be enslaved for a fixed period, provided some trace of His deliverance of them should remain.

In a word, He simply chose to apply this preventive measure so that slavery would not altogether extinguish the recollection of His grace, although He allowed it to be smothered in this way, as it were.

Therefore, so that cruel masters would not trust that their tyranny could be exercised with impunity, Moses reminds them that they had to do with God, who will eventually appear as its avenger.

Although the political laws of Moses are no longer in operation, still the analogy is to be preserved, so that the condition of those who have been redeemed by Christ’s blood will not be worse among us than that of the ancient people of old. Paul’s exhortation refers to this:

You masters, forbear threatening your slaves, knowing that both your and their Master is in heaven.¹⁵² (Ephesians 6:9)

¹⁵² See Margin of A. V.