What does 2 Peter 3:15 mean?

It's understandable that God's people would be eager to get to the day of the Lord. Saved believers want to see the new heaven and new earth. That's especially true in our times of suffering, and it is exactly what we should be longing for (Colossians 3:1–4).

Unlike the false teachers, however, Christians must not view the seeming delay in the coming of Christ as evidence that God is unloving or unfaithful or has broken His promise. Instead, as he did in verse 9, Peter again writes that any such delay is motivated only by God's patience. What we are tempted to think of as God waiting too long is really an expression of His desire to bring salvation to as many as possible. God's timing is motivated by love, not indifference.

Peter recognizes here that Paul has written something similar. Maybe he had in mind Romans 2:4, where Paul mentions God's patience and says that God's kindness is meant to lead to repentance. In any case, Peter acknowledges that Paul's wisdom comes from God and calls Paul a beloved brother. This is helpful to us because it confirms what is already clear from a careful reading of the New Testament: The inspired writings of each of the books establish and support each other. Peter, Paul, and the other writers all wrote the words of God through the inspiration of the Holy Spirit (2 Timothy 3:16).

None of the apostles were sinless men themselves though. Writing in one of his letters, Paul said that he rebuked Peter "to his face" at one point for sinful hypocrisy (Galatians 2:11–14). All the same, near the end of Peter's life, he speaks warmly of his brother Paul and affirms Paul's authority to speak on behalf of God as a full apostle.