Is there more to Christianity than practicing morality and supporting a church? Many think not, but there is. Christianity is a new life, consisting of new relationships with God, men, and things; and it all springs from one source—a unique link between the Christian and his Master, Jesus Christ.
The New Testament makes this quite clear, but talks of the link itself in language that is startling and hard to pin down. Union with Christ is affirmed in terms that sound too strong to be true. Thus, Paul says that “Christ … is our life” (Colossians 3:4), and “I live; yet not I, but Christ liveth in me” (Galatians 2:20); and he speaks of Christians doing and experiencing literally everything in Christ, and of baptized persons as having put on Christ (Galatians 3:27). So, too, Jesus says, “Abide in me, and I in you … I am the vine, you are the branches” (John 15:4ff.). What sort of link can it be that prompts such statements? – James I. Packer
Growing in Christ (Wheaton, IL; Crossway Books 1994) p. 119.