What does God give us at new birth? He gives us a new heart, a heart of flesh and not of stone (Ezek. 11:19). Then He says that He will write His Word on that heart (Heb. 8:10) and put His law in that heart (Heb. 10:16). "The heart" refers to the whole of the inner man, the mainspring of one's life. A man lives according to the dictates of his heart. Out of the heart the mouth speaks (Matt. 12:34). If our hearts are sinful, the only thing that can come out of our lives is sin. If our hearts are pure, goodness will be the result.
The only place we can get this new heart is from God, and He gives it by giving Himself when He comes to abide within our hearts. It is union with God by the Spirit, and the Lord says it is like a new birth, because we become a new creation at that time. The whole inner man is changed, made new by God. This is the one divine work of grace by which we are made one with God and baptized into the body of Christ.
But what we want to see here is that although God gives us a new heart or disposition at new birth, the outward man (our body and soul) are not made new. They were not sinful in themselves, but they have been instruments of sin up to that time, and will bear its marks. Now these faculties must be given over to God, and this is done through obedience. This is what is described in Romans 12:1,2. It is an active place, and does not happen automatically. God has done His part by giving us a new heart and bringing us into union and fellowship with Himself. But from that foundation it is our responsibility, through obedience to the Holy Spirit and the living Word being written on our hearts, to see our whole man set aside to God as a living sacrifice.
"Therefore lay aside all filthiness and overflow of wickedness, and receive with meekness the implanted word (or 'engrafted word') which is able to save your souls. But be doers of the word, and not hearers only, deceiving yourselves" (James 1:21,22). The engrafted word is the word which is made part of us (the "whole man") as we do the word. Hearing the word in our minds may be a beginning place, and hearing the living word in our hearts will author faith to move in God. But until that living word is acted upon, it does not take root in our lives and profit us. It is the doing of the word that strengthens us and begins to mature our expression of Christ.
It is here that so many fall short. They rejoice in the new heart, the new desires, and the new song that God has put within their hearts. The feelings that go with this are wonderful, and it seems like heaven has come to earth. But so often the joy is short-lived, because immediately an issue of life comes before them. The effects of the past life of sin stare them in the face. They are surprised, because they thought that Christ made everything new--yet here is some of the old. What then did Christ make new?
As seen above, Christ has made our relationship with God new, the heart new, and the ability new. But now from this new heart and new ability from God, situations of life must be dealt with. An undisciplined mind must be brought under the control of the Spirit. A weak and lazy body must be strengthened through exercise. An undisciplined and undirected family must be given direction and training. These and many other things must be dealt with through active obedience to God.
If we do not deal with these things, the weakness that results will sooner or later overtake us and snuff out the life of God. We will become disheartened, begin to take our eyes off Christ and become entangled again in worldly things. Our love will grow cold, and the things of earth will loom large once again. Why? Because we did not let the word take root in us through active obedience. We thought everything was done when we were born again. Is everything done when a baby is born? Life has only begun. The real labor comes in the long pull. Here is where we need the power of God. God is looking for finishers.
How is the physical body strengthened? Is it not through active exercise, pressing forward towards a goal? How is spiritual character formed in a man? Is it not through active exercise in the Spirit? It is not produced by sleeping, or by waiting on God to do something more. God has involved us, and it is only as our will (our whole man active) is placed in God's will in every area of our life, that we will begin to find a maturing expression of Christ, and see spiritual strength come to our lives. Although God has made every provision in Christ and the Holy Spirit, we must walk in every situation, every detail of life. We are not strengthened by dreaming about Christ. We are strengthened as we obey Christ. This is where we learn Christ, and this is where Christ is glorified in our lives. This is where godly character is built in our lives, and this is where we must be diligent.
However, we are not laboring on our own, but it is God at work within us, both to will and do His good pleasure (Phil. 2:13). The doing is obedience. Do we see the importance?