“For this very reason, make every effort to supplement your faith with virtue” (2 Peter 2:5a). Saint Peter admonishes them to give evidence of their faith with good works. Since such a great blessing has been given to you through faith that you truly have everything that is God’s, he wants to say, add to this, be diligent, do not be lazy, supplement your faith with virtue; that is, let your faith break forth before the people, in order that it may be helpful, busy, powerful, and active, and may do many works and not remain sluggish and sterile. You have a good inheritance and a good field. But see to it that you do not let thistles or weeds grow in it.
“And virtue with knowledge” (v. 5b). In the first place, understanding, or knowledge, means to lead one’s outward life and practice the virtue of faith in a sensible manner. For one should restrain and curb the body, in order that it may remain sober, alert, and fit for what is good. One should not hurt it too much and slay it, as some mad saints do. For even though God loathes the sins that remain in the flesh, yet He does not want you to slay your body on this account. You should check its wickedness and wantonness, but this does not mean that you should destroy or injure it. You must give it food and necessities, in order that it may remain healthy and alive.
In the second place, understanding also means to lead a fine, sensible life and to act judiciously in external matters, in matters of diet and the like. One should not do anything imprudently, and one should not give offense to one’s neighbor.
“And knowledge with self-control” (v. 6a). Self-control applies not only to eating and drinking; it is moderation in all circumstances of life, in words, deeds, and bearing. One should not live extravagantly. Excess in adornment and dress should be avoided, and no one should make himself conspicuous by being haughty and arrogant. But Saint Peter refrains from fixing a rule, a standard or aim, pertaining to this …. In Christendom it will not do to issue laws, so that there is a general rule pertaining to self-control. For people are not alike. One is strong, another is weak by nature, and no one is always as fit in every respect as the other person is. Therefore everyone should learn to know himself, what he can do and what he can stand.
“And self-control with steadfastness” (v. 6b). This is what Saint Peter wants to say: If you lead a temperate and sensible life, you should not suppose that you will live without trials and persecutions. For if you believe and lead a good, Christian life, the world will not let you alone. It must persecute you and be your enemy. You must bear this with patience, which is a fruit of faith. “And steadfastness with godliness” (v. 6c). This means that in our whole outward life, in what we do or suffer, we should conduct ourselves in such a way that we serve God and do not seek our own glory and advantage. It means that God alone must be praised by what we do and that we must act in such a way that one can see that we do everything for God’s sake.
“And godliness with brotherly affection” (v. 7a). This love extends to both friends and enemies, also to those who do not act in a friendly and brotherly way toward us. Thus here Saint Peter has expressed in a few words what belongs to a Christian life and what the works and the fruits of the faith are, namely, knowledge, self-control, patience, a God-fearing life, brotherly affection, and kindness to everybody.
“For if these things are yours and abound, they keep you from being ineffective or unfruitful in the knowledge of our Lord Jesus Christ” (v. 8). That is, if you do works of this kind, you are on the right path and have a true faith, and the knowledge of Christ is active and fruitful in you. Therefore see to it that you do not make light of this. Hold your body in subjection, and do for your neighbor as you know what Christ has done for you.
“For whoever lacks these things is blind and shortsighted and has forgotten that he was cleansed from his old sins” (v. 9). He who does not have such a supply of the fruits of faith gropes about like a blind person and lives in such a way that he does not know what his plight is. He does not have the true faith …. Therefore he goes along and fumbles in uncertainty, like a blind man on the road. He forgets that he has been baptized and that his sins have been forgiven. He becomes ungrateful and a lazy and careless person who takes nothing to heart and neither takes hold of nor tastes such great grace and blessings.
With this exhortation Saint Peter wants to incite and urge us who believe to do the works with which we should prove that we really have faith. He always insists that faith alone justifies. For where there is this faith, the works must follow. “Therefore, bretheren, be the more zealous to confirm your call and election” (v. 10a).
Indeed the election and God’s eternal foreordination is firm enough in itself and requires no confirmation. The call is also strong and firm. For he who hears the Gospel, believes in it, and is baptized, is called and will be saved. Now since we too, are called, we must be zealous, says Peter, to confirm this call and election for ourselves, not only for God.
If you want to be sure [of your election], you must adopt the method Saint Peter suggests here. Your own experience must teach you this. If your faith is well exercised and applied, you will finally gain assurance, and this will keep you from falling.