It is a most grievous threatening, when he says, that all who seek to elevate themselves, shall have God as their enemy, who will lay them low. But, on the contrary, he says of the humble, that God will be propitious and favorable to them. We are to imagine that; God has two hands; the one, which like a hammer beats down and breaks in pieces those who raise up themselves; and the other, which raises up the humble who willingly let down themselves, and is like a firm prop to sustain them. Were we really convinced of this, and had it deeply fixed in our minds, who of us would dare by pride to urge war with God? But the hope of impunity now makes us fearlessly to raise up our horn to heaven. Let, then, this declaration of Peter be as a celestial thunderbolt to make men humble.

But he calls those humble, who being emptied of every confidence in their own power, wisdom, and righteousness, seek every good from God alone. Since there is no coming to God except in this way, who, having lost his own glory, ought not willingly to humble himself?

John Calvin’s Commentary on 1 Peter 5:5