31 Perhaps by the heavens we here may understand, without being far-fetched, the righteous themselves, the saints of God, abiding in whom God has thundered in His commandments, lightened in His miracles, watered the earth with the wisdom of truth, for “The heavens have declared the glory of God.” But shall they perish? Shall they in any sense perish? In what sense? As a garment. What is, as a garment? As to the body. For the body is the garment of the soul; since our Lord called it a garment, when He said, “Is not the life more than meat, and the body than raiment?” How then does the garment perish?
“Though our outward man perish, yet the inward man is renewed day by day.” They then shall perish: but as to the body: “But You shall endure.”...Such heavens therefore shall perish; not, however, for ever; they shall perish, that they may be changed. Does not the Psalm say this? Read the following: “They shall all wax old as does a garment; and as a vesture shall Thou change them, and they shall be changed.” You hear of the garment, of the vesture, and do you understand anything but the body?
We may therefore hope for the change of our bodies also, but from Him who was before us, and abides after us....“But You are the same, and Your years shall not fail”. But what are we to those years with these beggarly years? And what are they? Yet we ought not to despair. He had already said in His great and exceeding Wisdom, “I Am That I Am;” and yet He says to console us, “I am the God of Abraham, and the God of Isaac, and the God of Jacob:” and we are Abraham's seed: even we, although abject, although dust and ashes, trust in Him.
We are servants: but for our sakes our Lord took the garb of a servant: for us who are mortal the Immortal One deigned to die, for our sakes He showed His example of resurrection. Let us therefore hope that we may reach these lasting years, in which days are not spent in a revolution of the Sun, but what is abides even as it is, because it alone truly Is.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)