What does the Bible say about the formation of Christ in believers?

In Galatians 4:19, the Apostle Paul expresses his deep concern for the Galatian churches, stating, 'My little children, of whom I travail in birth again until Christ be formed in you.' This verse emphasizes that the formation of Christ within believers is a spiritual process where they are transformed by the Holy Spirit, inherently revealing Christ's character and nature in their lives. It is indicative of spiritual birth and growth, where believers are not just externally religious but have the very life of Christ exhibited in them as they abide in faith and grace.