I Corinthians 2:14, II Corinthians 4:18
God has given each of us an eternal spirit. Our spirit is the eternal part of our being, that which will never pass away, and will carry us to one of two eternal destinations—eternal life or eternal death.
True life is communion with God, fellowship, relationship, friendship, marriage with Him. Final death is divorce and separation from God, a relationship that can never be, hopeless and eternal denial of His love and authority. Our spirit is what can only be filled by God’s Spirit; it longs for the relationship while on earth, finds fulfillment in heaven, but is left horribly empty and needy in hell, the eternal separation from God. In hell, temporary fulfillment will never be enough. In heaven, fulfillment and love will never be lacking, for we will have received our spirit’s desire—to be in the presence of the Father.
When we allow God’s Spirit to dwell in us, to fill the vessel within us, we belong to Him. At that point, we will be in Him and He will be in us. (If we do not, we do not belong to Christ and are destined for eternal separation from Him. “Depart from me, ye worker of iniquity; I never knew you!”—Matt. 7:23. For then eternal judgment will be rendered, and all will be made known of all.) When we allow Christ’s Spirit to consume us, what goes on in the flesh, the temporal, the physical, will not matter. We will be dead to all that once held us captive, but we will be alive in Christ, because He has fulfilled the law that we could not, and has put His righteousness on us, making us pure and worthy.
If life is the result of living by the Spirit, what is life? Communion with God. Fellowship. A whole-hearted relationship with Him. Either our flesh or our spirit will win out over the other. If we feed our flesh and indulge in the things that Galatians 5 condemns, our flesh will win out, but the temporary pleasure and fulfillment they provide are not worth the results of eternal death and separation from the Father. If we indulge in the things of the Spirit, our spirit will win out, and the eternal results cannot be matched by any other.