There is so much to unpack in this commandment that we will have to go very slowly.
The Fourth Commandment deals with Shabbat, the Sabbath, and appears in two forms in the Bible. The first is found in our Exodus text:
Remember the sabbath day and keep it holy. Six days you shall labor and do all your work, but the seventh day is a sabbath of HaShem your God: you shall not do any work—you, your son or daughter, your male or female slave, or your cattle, or the stranger who is within your settlements. For in six days HaShem made heaven and earth and sea, and all that is in them, and He rested on the seventh day; therefore HaShem blessed the sabbath day and hallowed it. (Exodus 20:8-11)
The second occurs in Deuteronomy where the Israelites are commanded to “observe” rather than to “remember” the Sabbath, and offers a different rationale for doing so: You shall remember that you were a slave in the land of Egypt, and HaShem your God brought you out from there with a mighty hand and an outstretched arm; therefore HaShem your God commanded you to keep the Sabbath day (Deuteronomy 5:16). I take these changes very seriously.
The logic of the Exodus version is clear: God rested on the seventh day of creation, so you rest on the seventh day of the week. The logic of the Deuteronomy version is apparent only if we assume it is speaking to a different time and situation, which I believe it is.
The shift from “remembering” to “observing” suggests that the Deuteronomy text comes at a time when the people were having trouble extending the rights of Shabbat to slaves. This is why the text links Sabbath observance to the Jew’s own slave experience: it is trying to soften their hearts that they might allow their slaves to rest on Shabbat.
The fact that the Bible condones slavery in the first place is problematic, but there is nothing we can do about that. The Bible does the best it can to protect slaves from abuse, but it cannot abolish slavery itself because slavery was too central to human socio-economic-political reality. As a human document, the Bible cannot demand what humans cannot imagine, and a world without slaves was at that time unimaginable.
But the Bible can imagine, and in fact legislate, a world without abuse of slaves and others who are powerless in society: widows, children, orphans, strangers, etc. This is no small thing. And, thousands of years later, we have yet to create a society in which such abuse is absent. I say this not to excuse the Bible for its acceptance of slavery, but to remind us of how revolutionary even this flawed document can be.
There is so much more to say, but let me stop here and invite you to jump in.