Apostle Paul was writing here to a church he did not start, and he was giving them the foundation of Christianity, which is Christ, our life. All throughout this letter he enforces their identity, saying things like “Christ in you”, “Christ, our life”, “ye have put on the new man”, “Christ is all, and in all” etc. Our identity in Christ is actually the main theme of this letter. Why is this important?

The growth of the knowledge of your identity brings greater levels of grace (2 Peter 1:2), or it brings transformation into your potential in Christ (Colossians 3:10, 2 Corinthians 3:18), and this growth is conditioned by where you look. Hebrews 12:2 says that our eyes should look unto “Jesus the author and finisher of our faith”. So, you see, Apostle Paul was trying to have the colossians root their faith in their identity in Christ.