John Calvin Commentary Exodus 23:12

"Six days thou shalt do thy work, and on the seventh day thou shalt rest; that thine ox and thine ass may have rest, and the son of thy handmaid, and the sojourner, may be refreshed." — Exodus 23:12 (ASV)

Six days you shall do your work. In this passage, the incidental use of the Sabbath is again referred to, although it is no inherent part of its original institution, namely, that by this means the family and the cattle shall also be benefited. There is no impropriety in reckoning this among the other blessings which enhance the value of the Sabbath, although it is a portion of the Second Table.

And we know that this unrefined people required to be attracted by every possible means to present cheerfully to God the worship due to Him. The sum, therefore, is that they were thus to testify not only their piety towards God, but also their kindness towards their servants.

I have already shown that their authority as masters was to be exercised in moderation by them, if they were mindful of their former condition, since they also had been servants in Egypt. If anyone should suppose that the argument does not hold good, because they were oppressed by cruel and dreadful tyranny, the reply is easy: that all the better could they determine from their own feelings how detestable and intolerable a thing cruelty is.