The fourth commandment is a transitional one in that it speaks to our relationship with bot God and our fellow human beings. We often think of Shabbat in terms of a day of rest, but as Leo Baeck points out, keeping Shabbat holy involves much more:
"The Sabbath does not mean a mere not working, nor an empty idleness. It connotes something positive. It has guided the soul unto its mystery, so that it is not a day that just interrupts, but a day that renews, speaks through it, of something eternal. It is the expression of a direction for life and not just an instituted day of rest. If it were only that, or if it became that, its essence would be taken from it. It would then be only a hollow shell."