In the second chapter of Peter’s first epistle, he continues to emphasize the believer’s holiness. That is, believers need to be different from the society in which they dwell. Long-story-short, Peter tells his readers, the Jews of the Diaspora in Asia Minor (1Peter 1:1), since they had been saved through a second birth to become the children of God (1Peter 1:23), and since they refer to God as Father (1Peter 1:17), they need to be different from the world around them. This would be especially so concerning those who intend to do evil against them (1Peter 2:1). God is different, incomparable (Isaiah 46:5), which is the essence of his attribute of holiness. So, when he calls his children to be holy, because he is holy (Leviticus 14:44-45; cf. 1Peter 1:16), he means he expects them to be different or separate from the world around them. His children must not allow themselves to be conformed to the mold (i.e. behavior philosophies, goals, knowledge etc.) of the world. Rather, be separate to serve their holy Father.
The sins mentioned in 1Peter 2:1 are relational sins, having to do with how one treats others. Peter doesn’t want his readers to engage in such behavior toward their neighbors, but especially towards one another. However, and more to the point of Peter’s letter, I think there is reason to believe that these very sins were committed against the churches in Asia Minor, and were committed against believers in their current trail (persecution).
Let’s ask ourselves a question. What would the persecution in Asia Minor look like, if it were begun by Annas, the high priest of Jerusalem, the same man who was responsible for the first persecution against the Church that began with Stephen? The works of the flesh mentioned in verse-1 (malice/spying, guile/trickery, hypocrisies/pretending, envies/ill will, evil speaking/defamation) parallel how Annas had originally dealt with the nascent Church. He sent in spies who lied about their belief in Christ (Acts 5:1, 13), pretending to be believers (cf. Galatians 2:4). They set up traps in order to defame believers and get them in trouble (Acts 6:11-14).
At first, one might think that Peter’s advice to his readers to desire the sincere milk of the word (1Peter 2:2), contradicts Paul at 1Corinthians 3:1-2 (cf. Hebrews 5:12-13), and may even go as far as saying that Peter intends to keep his readers immature (naive) in order to preserve their innocence. But, this is not the case here, and there is no contradiction with Paul. Peter is not speaking with babes in Christ, but children of God. He is not endorsing permanent immaturity but, rather, has in mind that one shouldn’t behave toward others as one has been treated by others (cf. Matthew 10:16). Don’t behave as a wolf, but do be wise as a serpent. Paul, also, encourages this attitude (cf. 1Corinthians 14:20).
With an obvious reference to being born again (1Peter 1:23), Peter tells his readers to eagerly desire genuine spiritual milk – a spiritual drink (cf. Isaiah 55:1 and 1Corinthians 10:4). Why? It is because one’s first temptation when treated badly is to respond in kind. Instead, if the one persecuted were to respond with the basics of his faith, he would be offering spiritual milk to his persecutors, who are not exercised in spiritual matters relating to Christ. Rather than responding in kind (1Peter 2:1) behave contrarily. If one was a gazing stalk or spied upon, forgive and overlook the malicious behavior of his enemy. If one was treated with deceit, respond again with forgiveness. Treat those who acted under pretense with a genuine spirit of kindness. Be generous with those who have acted out of greed and envy, and seek to find something praiseworthy for those who have lied about believers and sought to defame their good name. Such may be sincere, spiritual milk, but it is offered to those who have acted contrary to mature behavior. Those who have exercised themselves according to Peter’s advise are mature believers in Christ, and not only so, but they would be different from the world around them, as the Father is different, and that’s important.