Jude 20-21 But you, beloved, building yourselves up on your most holy faith, praying in the Holy Spirit, 21 keep yourselves in the love of God, waiting anxiously for the mercy of our Lord Jesus Christ to eternal life.
1. Colossians 1:3-4 "We give thanks to God, the Father of our Lord Jesus Christ, praying always for you, 4 since we heard of your faith in Christ Jesus and the love which you have for all the saints."
The book of Colossians is all about finding our fulfillment in the supremacy of Jesus Christ. He is enough, period. In this passage we find the two-fold focus of spiritual maturity: faith in Jesus Christ and love for the saints.
2. Colossians 1:10-11 "so that you will walk in a manner worthy of the Lord, to please Him in all respects, bearing fruit in every good work and increasing in the knowledge of God; 11 strengthened with all power, according to His glorious might, for the attaining of all steadfastness and patience; joyously."
The underlined words in this text speak to the very subject of spiritual maturity. Nearly fifty times we find reference to walking with God in the scriptures. All of the tributaries that flow from that stream (bearing fruit, growing, etc) find their source in Jesus Christ.
3. Colossians 2:6-7 "Therefore as you have received Christ Jesus the Lord, so walk in Him, 7 having been firmly rooted and now being built up in Him and established in your faith, just as you were instructed, and overflowing with gratitude."
This text here continues on the theme of Colossians 1:10-11. The book of Colossians, along with the book of Hebrews, are two books in the New Testament that deal specifically with finding one's fulfillment and maturity in the supremacy of Jesus Christ.
4. Colossians 3:16 "Let the word of Christ richly dwell within you, with all wisdom teaching and admonishing one another with psalms and hymns and spiritual songs, singing with thankfulness in your hearts to God."
This particular passage is significant in that the word "word" could be taken to either refer to the written word - the Bible, or the living word - Jesus Christ. One of the hallmarks of spiritual maturity is in making one's life a palatial dwelling place for the Lord and His word. The more central the Bible becomes to our everyday thoughts and lives, the more likely we are growing in spiritual maturity.
5. Colossians 4:17 Conduct yourselves with wisdom toward outsiders, making the most of the opportunity.
Spiritual maturity not only has to do with how we relate to the Lord and how we take care of ourselves but also in how we relate to other people. "Making the most" of every opportunity means that even in the most extreme circumstances, we take what we have and use it for the glory of God. Over time we discover that if anyone wants to be Godly in Christ Jesus, they should expect to suffer. (see 2 Timothy 3:12)