Calvin commenting on Psalm 92:
The reason why the Psalmist appropriated this psalm to the Sabbath is sufficiently obvious. That day is not to be holy, in the sense of being devoted to idleness, as if this could be an acceptable worship to God, but in the sense of our separating ourselves from all other occupations, to engage in meditating upon the Divine works. As our minds are inconstant, we are apt, when exposed to various distractions, to wander from God. We need to be disentangled from all cares if we would seriously apply ourselves to the praises of God. The Psalmist then would teach us that the right observance of the Sabbath does not consist in idleness, as some absurdly imagine, but in the celebration of the Divine name.
Source: http://www.puritanboard.com/threads/not-in-idleness-but-in-separation.91760/, Comment 1