The Apostle Peter's words concern the application of various characteristics (2 Peter 1:5-7) amongst people who are in Christ. A productive servant of God will display these qualities. We have been called to mature in faith now that we have been renewed by the Holy Spirit. If we faithfully serve God, then that can only bolster our confidence that we are His children. Our assurance of salvation rests on the solid foundation of Jesus Christ.
The two epistles of Peter are written on the assumption that the intended audience has already been justified before God by faith. The object of emphasis is on people who have believed on the gospel and are loved by Him (1 Peter 2:7; 2 Peter 1:1). The highlighted passage of Scripture gives us a picture of what sanctification looks like. Calling and election are gifts according to God's eternal plan (Romans 9:11-16; 2 Timothy 1:9).