John Calvin Commentary 1 Peter 1:24

"For, All flesh is as grass, And all the glory thereof as the flower of grass. The grass withereth, and the flower falleth:" — 1 Peter 1:24 (ASV)

For all flesh. He aptly quotes the passage from Isaiah to prove both points: that is, to make it evident how fading and miserable man's first birth is, and how great is the grace of the new birth. For as the Prophet there speaks of the restoration of the Church, to prepare the way for it, he reduces people to nothing so that they would not flatter themselves.

I know that some wrongly interpret the words to mean something else. Some explain them as referring to the Assyrians, as though the Prophet said that there was no reason for the Jews to fear so much from flesh, which is like a fading flower. Others think that the vain confidence which the Jews placed in human aid is being rebuked.

But the Prophet himself disproves both these views by adding that the people were as grass, for he expressly condemns the Jews for vanity, to whom he promised restoration in the name of the Lord. This, then, is what I have already said: until their own emptiness has been shown to people, they are not prepared to receive the grace of God. In short, this is the Prophet's meaning: as exile was like death to the Jews, he promised them a new consolation, namely, that God would send prophets with a command of this kind. The Lord, he says, will yet say, “Comfort ye my people;” and that in the desert and the waste, the prophetic voice would yet be heard, so that a way might be prepared for the Lord (Isaiah 40:6).

And as the obstinate pride that filled them had to be purged from their minds so that access might be open for God, the Prophet added what Peter relates here concerning the vanishing glory of the flesh. What is man? he says — grass; what is the glory of man? the flower of the grass. For as it was difficult to believe that man, in whom so much excellence appears, is like grass, the Prophet made a kind of concession, as though he had said, “Indeed, grant that flesh has some glory; but so that it does not dazzle your eyes, know that the flower soon withers.” He afterwards shows how suddenly everything that seems beautiful in people vanishes, even through the blowing of the Spirit of God.

By this he implies that a person seems to be something until he comes to God, but that his whole brightness is as nothing in His presence. In a word, his glory is in this world and has no place in the heavenly kingdom.

The grass withereth, or, has withered. Many think that this refers only to the outward man, but they are mistaken, for we must consider the comparison between God’s word and man. For if he meant only the body and what belongs to the present life, he should have said, in the second place, that the soul was far more excellent.

But what he sets in opposition to the grass and its flower is the word of God. It then follows that in man nothing but vanity is found. Therefore, when Isaiah spoke of flesh and its glory, he meant the whole man, such as he is in himself; for what he ascribed as peculiar to God’s word, he denied to man.

In short, the Prophet speaks of the same thing as Christ does in John 3:3: that man is wholly alienated from the kingdom of God, that he is nothing but an earthly, fading, and empty creature, until he is born again.