John Calvin Commentary 2 Peter 1:5

"Yea, and for this very cause adding on your part all diligence, in your faith supply virtue; and in [your] virtue knowledge;" — 2 Peter 1:5 (ASV)

And besides this. As it is an arduous work and one of immense labor to put off the corruption that is in us, he instructs us to strive and make every effort for this purpose. He intimates that no place is to be given to sloth in this case, and that we ought to obey God who is calling us, not slowly or carelessly, but with alacrity; as though he had said, “Put forth every effort, and make your exertions manifest to all.” — For this is what the participle he uses signifies.

Add to your faith virtue, or, Supply to your faith virtue. He shows for what purpose the faithful were to strive: that is, that they might have faith adorned with good morals, wisdom, patience, and love. Then he intimates that faith should not be naked or empty, but that these are its inseparable companions. To supply to faith is to add to faith. There is not here, however, properly a gradation in terms of meaning, though it appears so in terms of wording; for love does not follow patience in sequence, nor does it proceed from it. Therefore, the passage is to be explained simply in this way: “Strive that virtue, prudence, temperance, and the things that follow, may be added to your faith.”

I take virtue to mean an honest and rightly formed life; for it is not here ἐνέργεια (energy or courage), but ἀρετὴ (virtue, moral goodness). Knowledge is what is necessary for acting prudently, for after having stated a general term, he mentions some of the principal endowments of a Christian. Brotherly-kindness, φιλαδελφία, is mutual affection among the children of God. Love extends wider, because it embraces all mankind.

However, it may be asked here whether Peter, by assigning to us the work of supplying or adding virtue, thereby extolled the strength and power of free will? Those who seek to establish free will in humanity indeed concede to God the first place—that is, that He begins to act or work in us—but they imagine that we cooperate at the same time, and that it is thus due to us that the movements of God are not made void and ineffective.

But the perpetual doctrine of Scripture is opposed to this delirious notion, for it plainly testifies that right feelings are formed in us by God and are made effective by Him. It also testifies that all our progress and perseverance are from God. Besides, it expressly declares that wisdom, love, patience, are the gifts of God and the Spirit.

When, therefore, the Apostle requires these things, he by no means asserts that they are in our power, but only shows what we should have and what should be done. And as for the godly, when conscious of their own weakness, they find themselves lacking in their duty, nothing remains for them but to flee to God for aid and help.