John Calvin Commentary Romans 8:21

"that the creation itself also shall be delivered from the bondage of corruption into the liberty of the glory of the children of God." — Romans 8:21 (ASV)

Because the creation itself, etc. He shows how the creation has in hope been made subject to vanity; that is, since it will one day be made free, according to what Isaiah testifies, and what Peter confirms still more clearly. It is then indeed fitting for us to consider what a dreadful curse we have deserved, since all created things in themselves blameless, both on earth and in the visible heaven, undergo punishment for our sins; for it has not happened through their own fault that they are liable to corruption. Thus the condemnation of mankind is imprinted on the heavens, and on the earth, and on all creatures. Hence it also appears to what excellent glory the sons of God will be exalted, for all creatures will be renewed to amplify it and to make it illustrious.

But he does not mean that all creatures will be partakers of the same glory with the sons of God, but that they, according to their nature, will be participators of a better condition; for God will restore to a perfect state the world, now fallen, together with mankind. But what that perfection will be, as to beasts as well as plants and metals, it is not fitting nor right for us to inquire too curiously; for the chief effect of corruption is decay. Some subtle men, but hardly sober-minded, inquire whether all kinds of animals will be immortal; but if free rein is given to speculations, where will they eventually lead us? Let us then be content with this simple doctrine—that such will be the constitution and the complete order of things, that nothing will be deformed or fading.