John 3:3-6 Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God. Nicodemus saith unto him, How can a man be born when he is old? can he enter the second time into his mother’s womb, and be born? Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God. That which is born of the flesh is flesh; and that which is born of the Spirit is spirit.
The most complicated and misunderstood issues in the intended design is the third part, the spirit. The reason is both simple and complicated. Up until the time we are reborn in the spirit, we have had years of nothing but the two parts of the intended design, the body and soul. During this period of time the body and soul have been cooperating with selfish interests. The body wants what it wants to satisfy its design, the soul is ever searching to satisfy those needs with a vested interest in interacting with the environment to meet those needs and hoping to satisfy those needs with a sense of accomplishment.
Now the Spirit which is God takes up residence within the body. The Spirit is perfect in performance of design, He has to be, He is God. The role of the Spirit is to communicate with the soul all that Jesus Christ is and does in accomplishing the promises of His New Covenant. As God He has the power to enforce the will of God the Father. This includes having power to act as God without permission of the body and soul. The body and soul have no power over the Spirit.
Here in lies the battlefield of living a life in Christ, for the Spirit does not interfere with free will. The soul must choose to love God, Jesus Christ and act in accordance with original design to access all the promises of the New Covenant. That is obedience of faith.
Next is the issue of living by design, as God intended.