'Repent, for the kingdom of the heavens is at hand' (Matt. 3:2, 4:17, 10:7). This is a call for us to reconsider how we have been approaching our life, in light of the fact that we now, in the presence of Jesus, have the option of living within the surrounding movements of God’s eternal purposes, of taking our life into his life.
~Dallas Willard, The Divine Conspiracy
The Bible has a lot to say about spiritual formation. Below are just a few passages that encourage us in spiritual renewal; if you’re interested in learning more, Renovaré’s Life With God Bible provides a comprehensive perspective on spiritual formation throughout scripture.
2 Corinthians 3:18
And we, who with unveiled faces all reflect the Lord's glory, are being transformed into his likeness with ever-increasing glory, which comes from the Lord, who is the Spirit.
2 Corinthians 4:16
Therefore we do not lose heart. Though outwardly we are wasting away, yet inwardly we are being renewed day by day.
Ephesians 4:20-24
But that isn’t what you learned about Christ. Since you have heard about Jesus and have learned the truth that comes from him, throw off your old sinful nature and your former way of life…. Instead, let the Spirit renew your thoughts and attitudes. Put on your new nature, created to be like God—truly righteous and holy.
1 Tim 4:7-8
…train yourself to be godly. For physical training is of some value, but godliness has value for all things, holding promise for both the present life and the life to come.
Colossians 3:10-11
Each of you is now a new person. You are becoming more and more like your Creator, and you will understand him better. It doesn't matter if you are a Greek or a Jew, or if you are circumcised or not. You may even be a barbarian or a Scythian, and you may be a slave or a free person. Yet Christ is all that matters, and he lives in all of us.