Romans 8:9 (ESV) "You, however, are not in the flesh but in the Spirit, if in fact the Spirit of God dwells in you. Anyone who does not have the Spirit of Christ does not belong to him."If we are "not in the flesh, but in the Spirit" where are we? First off, we must ask: "What is in the flesh?" It is our inherited nature because we are human. It is a result of original sin, the disobedience of Adam. Being of the flesh is outside divine influence. It's living without the Spirit of Christ inside. It is doing what is right in our own eyes!
We know from scripture that the flesh is the idol of our human nature. A man or woman in the flesh sets themselves up as god and places that god before God. Those in the flesh do not necessarily abandon God, but place their own god before God. Never did Adam abandon God, but endeavored to become as God. In essence Adam worshipped two gods: The One True God and his own self. Because no one can serve two masters, one must have the allegiance.
This is essential! For one to be born-again, it's that god who is seen in the flesh, which must be made a living sacrifice (Romans 12:1). For one to be born-again, what people casually call "saved" is bringing that flesh to the altar and sacrificing it to God. It's giving up your human nature for a divine nature.
What is human nature? It's an inborn desire to pleasure oneself. The flesh is the medium of pleasure and is more than a dermal layer. The epidermis is merely the idol, but the god which lies within is much more terrible! The flesh is the composite of all human desires. We call that "the heart" and it's the heart which must be circumcised!
Jeremiah 4:4 (ESV) "Circumcise yourselves to the Lord; remove the foreskin of your hearts, O men of Judah and inhabitants of Jerusalem; lest my wrath go forth like fire, and burn with none to quench it, because of the evil of your deeds.”Abraham circumcised his foreskin as his signature to the Covenant that God made with him. He sealed the deal in his own blood in deference to God. That was symbolic of what he was doing inside! His heart was undergoing circumcision because he was giving up his human nature. It's that same nature that we give to God when we are born-again. Jeremiah even defined what born-again entails as the heart is circumcised: It's giving up your evil deeds! Jeremiah had the Spirit of God within him, but not then the Spirit of Christ because Christ has not yet died, let alone resurrected.
Giving up deeds means keeping God's Law. However, keeping the Law without a change in nature is works and salvation is by grace. Therefore, it's not keeping the Law which leads to salvation, but having the desire to please God by doing his will (Matthew 6:10). Hence, circumcision of the heart is a changed nature. The changed person who sacrifices himself, gives up the desire to sin. Therein, comes the struggle between the Spirit and the flesh: the former being willing and the latter being weak. God knows that our nature is weak, but he looks at the heart. Is it willing to be obedient? Remember, Adam's sin was disobedience. He desired to do what was right in his own eyes.
Being born-again is relinquishing our inborn desires. That does not guarantee success because we are still human. The foreskin has been removed from our heart, but the heart still remains. Thus, we struggle with the desires of the flesh because we're human. All our forebears knelt down to the flesh, and that's a genetic trait which is powerful. We can't do it by ourselves, but we're not alone. God in his wisdom left a Comforter to pull us through the desires of the flesh (John 14:16).
The Comforter, rendered "Helper" in the ESV, does just that. He helps us overcome the desires of the heart. He takes the place of the foreskin which we sacrificed. That foreskin is our personal will. God's will replaces our own. When we are born-again, that new person has relinquished his own will for God's will. In essence, his own god is no longer the object of worship. God alone is. The Spirit of God is the Helper. As such the Helper is God manifested by His Holy Spirit, his omnipresence everywhere.
The Spirit of Christ is specific. Jesus died, was resurrected, ascended to heaven and his Holy Ghost returned on the day of Pentecost, and appear as fire to those who received him. This coming of the Holy Ghost was significant because those gathered already had the Spirit of God. They had already sacrificed themselves to God as their hearts were circumcised of its foreskin. However, that was symbolic! The heart was still there.
I would suppose that the spiritual heart must be the soul. The soul itself is the cup which holds two things: emptiness or the Holy Ghost, that specific Spirit of God who suffered as Christ on the cross. Specifically, the Spirit of Christ which we call the Holy Ghost. He lives within our hearts if we have sacrificed our flesh at his altar. As such we are imbued (called "filled" erroneously) with Jesus - his Ghostly Presence.
It's necessary to know the difference between filled and imbued. Only Christ was full of the Holy Spirit. He was without sin. We're not. Therefore, because we are not God, sin still resides in our hearts because we can still relent to temptation, but Jesus lives there too. Just as a sponge soaks up water, our soul soaks up Spirit, but just as a sponge still has material substance, our hearts do as well. But a heart imbued with Christ's Spirit is much more spiritually healthy than a dirty spiritual sponge. Christ's presence in our hearts helps us because his Holy Ghost was tempted just as we are. He understands!
The heart which does not have the Spirit of Christ has not cut off the foreskin of the heart. That person has not yet truly sacrificed himself. That foreskin represents the willingness to be obedient to Jesus rather than a servant of the god of self. Before one is born-again that living sacrifice must be made. When we hold our spiritual breath and quit trusting in our self, and begin trusting Jesus for our salvation, then we are truly born-again. Before that can ever happen we must come to realize that as mere humans, we are not really gods, and can only have the hope of salvation because Jesus died in our place. We must accept Christ's grace. That's one thing we must DO before we become a new creation, one without the foreskin on our hearts and having the Spirit of Christ residing inside.