1 Peter 1:14

14As obedient children He first intimates that we are called by the Lord to the privilege and honor of adoption through the Gospel; and, secondly, that we are adopted for this end, that he might have us as his obedient children. For though obedience does not make us children, as the gift of adoption is gratuitous, yet it distinguishes children from aliens. How far, indeed, this obedience extends, Peter shews, when he forbids God’s children to conform to or to comply with the desires of this world, and when he exhorts them, on the contrary, to conform to the will of God. The sum of the whole law, and of all that God requires of us, is this, that his image should shine forth in us, so that we should not be degenerate children. But this cannot be except we be renewed and put off the image of old Adam.

Hence we learn what Christians ought to propose to themselves as an object throughout life, that is, to resemble God in holiness and purity. But as all the thoughts and feelings of our flesh are in opposition to God, and the whole bent of our mind is enmity to him, hence Peter begins with the renunciation of the world; and certainly, whenever the Scripture speaks of the renewal of God’s image in us, it begins here, that the old man with his lusts is to be destroyed.

In your ignorance The time of ignorance he calls that before they were called into the faith of Christ. We hence learn that unbelief is the fountain of all evils. For he does not use the word ignorance, as we commonly do; for that Platonic dogma is false, that ignorance alone is the cause of sin. But yet, how much soever conscience may reprove the unbelieving, nevertheless they go astray as the blind in darkness, because they know not the right way, and they are without the true light. According to this meaning, Paul says,

“Ye henceforth walk not as the Gentiles, in the vanity of their mind, who have the mind darkened, being alienated from the life of God, because of the ignorance that is in them.”
(Ephesians 4:17.)

Where the knowledge of God is not, there darkness, error, vanity, destitution of light and life, prevail. These things, however, do not render it impossible that the ungodly should be conscious of doing wrong when they sin, and know that their judge is in heaven, and feel an executioner within them. In short, as the kingdom of God is a kingdom of light, all who are alienated from him must necessarily be blind and go astray in a labyrinth.

We are in the meantime reminded, that we are for this end illuminated as to the knowledge of God, that we may no longer be carried away by roving lusts. Hence, as much progress any one has made in newness of life, so much progress has he made in the knowledge of God.

Here a question arises, — Since he addressed the Jews, who were acquainted with the law, and were brought up in the worship of the only true God, why did he charge them with ignorance and blindness, as though they were heathens? To this I answer, that it hence appears how profitless is all knowledge without Christ. When Paul exposed the vain boasting of those who wished to be wise apart from Christ, he justly said in one short sentence, that they did not hold the head. (Colossians 2:19.) Such were the Jews; being otherwise imbued with numberless corruptions, they had a veil over the eyes, so that they did not see Christ in the Law. The doctrine in which they had been taught was indeed a true light; but they were blind in the midst of light, as long as the Sun of Righteousness was hid to them. But if Peter declares that the literal disciples even of the Law were in darkness like the heathens, as long as they were ignorant of Christ, the only true wisdom of God, with how much greater care it behoves us to strive for the knowledge of him!