8 For if these things be in you, and abound, they make you that ye shall neither be barren nor unfruitful in the knowledge of our Lord Jesus Christ. 9 But he that lacketh these things is blind, and cannot see afar off, and hath forgotten that he was purged from his old sins. 10 Wherefore the rather, brethren, give diligence to make your calling and election sure: for if ye do these things, ye shall never fall: 11 For so an entrance shall be ministered unto you abundantly into the everlasting kingdom of our Lord and Saviour Jesus Christ.
If we have faith, virtue, knowledge, temperance, patience, Godliness, brotherly kindness, and charity we will grow in our understanding of our Lord. If we lack those things we are nearsighted spiritually and can only see our immediate circumstances not realizing that we have eternal life in Christ and were purged from our old sins. We will keep being devoured by them.
Peter calls Christians to make certain by possession of these traits that we are, indeed, Christians and belong to Christ. Paul also gives us proofs or fruit of having the Spirit of God inside of us.
Galatians 5:22 But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith, 23 Meekness, temperance: against such there is no law. 24 And they that are Christ’s have crucified the flesh with the affections and lusts. 25 If we live in the Spirit, let us also walk in the Spirit. 26 Let us not be desirous of vain glory, provoking one another, envying one another.
Ephesians 5:8 For ye were sometimes darkness, but now are ye light in the Lord: walk as children of light: 9 (For the fruit of the Spirit is in all goodness and righteousness and truth;) 10 Proving what is acceptable unto the Lord.
Paul also tells us to examine ourselves and the proofs of our faith.
2Corinthians 13:5 Examine yourselves, whether ye be in the faith; prove your own selves. Know ye not your own selves, how that Jesus Christ is in you, except ye be reprobates?
James made a similar statement to Peter’s about the carnal Christian’s forgetfulness.
James 1:23 For if any be a hearer of the word, and not a doer, he is like unto a man beholding his natural face in a glass: 24 For he beholdeth himself, and goeth his way, and straightway forgetteth what manner of man he was. 25 But whoso looketh into the perfect law of liberty, and continueth therein, he being not a forgetful hearer, but a doer of the work, this man shall be blessed in his deed. 26 If any man among you seem to be religious, and bridleth not his tongue, but deceiveth his own heart, this man’s religion is vain. 27 Pure religion and undefiled before God and the Father is this, To visit the fatherless and widows in their affliction, and to keep himself unspotted from the world.
It is amazing to understand this and then to see how many so-called conservative Christians are hateful, mean-spirited, greedy, materialistic, abusive, and selfish. Such Christians will regard their church attendance and how often they go “soul-winning” as an indication of how close they are to God and yet ignore these things the Bible clearly says they need. It is reminiscent of how the Jews considered their ritual observances as so important and missed what was important to God. Jesus said;
Matthew 23:23 Woe unto you, scribes and Pharisees, hypocrites! for ye pay tithe of mint and anise and cummin, and have omitted the weightier matters of the law, judgment, mercy, and faith: these ought ye to have done, and not to leave the other undone. 24 Ye blind guides, which strain at a gnat, and swallow a camel. 25 Woe unto you, scribes and Pharisees, hypocrites! for ye make clean the outside of the cup and of the platter, but within they are full of extortion and excess. 26 Thou blind Pharisee, cleanse first that which is within the cup and platter, that the outside of them may be clean also. 27 Woe unto you, scribes and Pharisees, hypocrites! for ye are like unto whited sepulchres, which indeed appear beautiful outward, but are within full of dead men’s bones, and of all uncleanness. 28 Even so ye also outwardly appear righteous unto men, but within ye are full of hypocrisy and iniquity.
This passage in 2Peter opens and closes with a call to diligence, serious and determined effort. See verse 5 previously mentioned.