Exodus 23:12

Six days thou shalt do thy work, and on the seventh day thou shalt rest, mainly by desisting from work, that thine ox and thine ass may rest, and the son of thy handmaid and the stranger may be refreshed. So the slaves and the strangers, as well as the domestic animals, were to be given a breathing spell once a week, the Sabbath thus serving not only religious, but also humanitarian ends.