John Calvin Commentary Psalms 78:39

"And he remembered that they were but flesh, A wind that passeth away, and cometh not again." — Psalms 78:39 (ASV)

And he remembered that they were flesh. Another reason is now brought forward why God had compassion on the people: his unwillingness to try his strength against humans, who are so constituted as to live only for a short period in this world and then quickly pass away. For the expressions used here denote the frailty that makes the human condition miserable.

Flesh and spirit are frequently contrasted in the Scriptures. This contrast appears not only when flesh means our depraved and sinful nature and spirit the uprightness to which God’s children are born again, but also when humans are called flesh because there is nothing firm or stable in them, as it is said in Isaiah: Egypt is flesh, and not spirit (Isaiah 31:3).

In this passage, however, the words flesh and spirit are used in the same sense—flesh meaning that humans are subject to corruption and decay, and spirit meaning that they are only a breath or a fleeting shadow.

As humans are brought to death by continual wasting and decay, the people are compared to a wind that passes away and, of its own accord, subsides and does not return again. When we have run our race, we do not begin a new life on earth, just as it is said in Job:

For there is hope of a tree, if it be cut down, that it will sprout again, and that the tender branch thereof will not cease. Though the root thereof wax old in the earth, and the stock thereof die in the ground; yet through the scent of water it will bud, and bring forth boughs like a plant. But man dieth and wasteth away; yea, man giveth up the ghost, and where is he? (Job 14:7)

The meaning, then, as we can now clearly perceive, is that God, in exercising his mercy and goodness, bore with the Jews, not because they deserved this, but because their frail and transitory condition called forth his pity and induced him to pardon them.

We will later find an almost similar statement in Psalm 103:13-16, where God is described as being merciful to us because he sees that we are like grass and that we soon wither and become dry like hay.

Now, if God finds in us nothing but misery to move him to compassion, it follows that it is solely his own pure and undeserved goodness that induces him to sustain us.

When it is affirmed that humans return not after they have finished the course of their lives in this world, this is not meant to exclude the hope of a future resurrection. For humans are considered here only as they are in themselves, and it is merely their earthly state that is being discussed.

Regarding the renewal of humans to the heavenly life, it is a miracle far surpassing nature. In the same sense, it is said in another place, His spirit goeth forth, and returneth not . This language implies that humans, when they are born into the world, do not bring with them the hope of future restoration; this hope must be derived from the grace of regeneration.