“It was very suitable for Solomon, who was endued with the spirit of wisdom in the affairs of government, to discourse of things which he knew and had experience about. In affirming that God governs the world and the life of man, he does so for two reasons.
First, whatever prosperous event may fall out to men, their ingratitude is instantly manifested by their ascribing it wholly to themselves. And thus God is defrauded of the honor which is His due.
Solomon, to correct such a perverse error, declares, that nothing happens prosperously to us except in so far as God blesses our proceedings.
Secondly, his purpose was to beat down the foolish presumption of men, who, setting God aside, are not afraid to undertake to do anything, whatever it may be, in exclusive reliance upon their own wisdom and strength.
Stripping them, therefore, of that which they groundlessly arrogate to themselves, he exhorts them to modesty and the invocation of God. He does not, however, reject either the labor, the enterprises, or the counsels of men. For it is a praiseworthy virtue diligently to discharge the duties of our office.
It is not the will of the Lord that we should be like blocks of wood, or that we should keep our arms folded without doing anything, but that we should apply to use all the talents and advantages which he has conferred upon us.
It is indeed true that the greatest part of our labors proceeds from the curse of God. And yet although men had still retained the integrity of their primitive state, God would have had us to be employed, even as we see how Adam was placed in the garden of Eden to dress it. (Genesis 2:15.)
Solomon, therefore, does not condemn watchfulness, a thing which God approves. He does not codemn men’s labor, by which when they undertake it willingly, according to the commandment of God, they offer to Him all acceptable sacrifice.
But lest, blinded by presumption, they should forcibly appropriate to themselves that which belongs to God, he admonishes them that their being busily occupied will profit them nothing, except in so far as God blesses their exertions.”
–John Calvin, Commentary on the Psalms, Volume 5 in Calvin’s Commentaries (Grand Rapids: Baker, 2001), 104-105. Calvin is commenting on Psalm 127:1.