[John Piper]
Union with Jesus Christ in His dying is the key to putting to death the deeds of the body. Our old self was crucified with Him in order that something practical might flow from that glorious union with Christ in His dying. How do you get unified with Christ? Faith alone, apart from works of the Law, unites you with Jesus so that He becomes your righteousness and your pardon and your death, so that something practical might succeed in your life - namely, the putting to death of what is dead. That's Christianity