Personally, it has been a help to meditate on this question in the middle of a chaotic Advent, "Why did Jesus take on human flesh?" Though the Bible offers many answers to this question, consider this: Jesus took on flesh in order to crucify our flesh.
There is a range of meanings for "flesh" in the New Testament. Sometimes it refers to a physical body (ex. 2 Cor. 4:11) while at others it refers to our way of life, under the dominion of sin, prior to conversion (ex. Rom. 8:6-8). My answer plays on this range of meaning because Jesus had a physical body, but was not a sinner.
In Galatians 5:24, Paul writes, "And those who belong to Christ Jesus have crucified the flesh with it passions and desires." Here, the "flesh" refers to our pre-converted existence---the old self under the dominion of sin. In this condition, we were both hostile to God and alienated from him, enslaved to the power of sin. But God has done something about our predicament. For those who belong to Christ, the flesh has been executed---may it rest in peace.
How did this happen? Is the flesh crucified after a lot of effort on our part? If so, what regimen enables this? Or does the flesh die in another way?
According to Paul, our flesh dies when we are united to Jesus in baptism. He is not speaking of a process, but rather an event. Consider Colossians 2:11-12:
In him also you were circumcised with a circumcision made without hands, by putting off the body of the flesh, by the circumcision of Christ, having been buried with him in baptism, in which you were also raised with him through faith in the powerful working of God, who raised him from the dead.
When we are joined to Jesus, we are crucified with him (Gal. 2:20). In other words, the violence done to Jesus' body is the same violence done to our flesh. So if Jesus died, and we are united to him, then our flesh has died as well. And, if Jesus rose, we have also risen to new life (and will rise physically one day)! This is one of the many gracious benefits God gives to those who are united to his Son, Jesus Christ. His death becomes our death, and his life, our life (Rom. 6:5-11; 8:1-11;j Col. 3:1-11). Life flows into us through Christ, our living Head (Col. 2:19; Eph. 4:15-16).
No Longer Enslaved
So what does this mean for us?
Chiefly, it means that we are no longer enslaved to sin (Rom. 6:7). We have been set free from the flesh's control (Rom. 7:5-6). Certainly, sin remains in us. But we are no longer subject to its tyranny. We are liberated into a new life---free to struggle against sin, no longer condemned to struggle under sin.
Given our daily experience, we don't always feel this way. In the 1990 romantic comedy Pretty Woman, writer J. F. Lawton brings our struggle to expression. Richard Gere, a lonely but powerful businessman, says to Julia Roberts, a prostitute hired for companionship, "I believe you a very bright and very special woman." She replies, "The bad things are easier to believe." This is our dilemma as well. The bad things---our feelings of hopelessness in sin---are easier to believe. As Roberts's character struggled to believe she was bright and special, we struggle to believe the objective realities that are true of us in Christ.
Fortunately, the accomplishments of God's grace do not bow to the whims of our feelings. If Jesus died, then our flesh is dead. If Jesus rose, then God has raised us to new life in the Spirit. That is the truth about the Christian.
This is where we must begin to battle sin. It begins in faith. In Romans 6:11, Paul instructs us to consider ourselves---an act of faith---as "dead to sin and alive to God in Christ." Indeed, justification and sanctification are by faith. Then, in the power of the Spirit, we advance to the front line, putting specific sins to death, in the full confidence that the power of the flesh has already been defeated. As Herman Ridderbos wrote, "They must fight their battle in the certainty that their enemy has been overcome" (Paul, 209). We cannot battle sin without first being liberated from the flesh through the death of Jesus.
So how do you consider yourself? Do you consider yourself dead to sin and alive to God? Or do you consider yourself forgiven but dead in sin? Friends, we are forgiven, counted righteous through faith in Jesus, and made alive in Christ (Eph. 2:4). You may deal every day with sin, but that sin does not reign over you. You are liberated from its power!
Relish this truth. Feast upon Christ in faith, and all that God promises to us in him. And, may the historical reality of Jesus' flesh, and the death he died, become the basis of a new reality in your life as you put to death the deeds of the body (Rom. 8:13).