Like God, we humans are spiritual beings. Unlike God, we are not just spirit; we are physical, corporeal bodies which are animated by spirit.
Imagine, if you will, a living body. Picture this body standing upright, but perfectly still. Every system in the body is functioning as it should: the heart is beating at 72 times a minute; the oxygen-carbon-dioxide exchange is going as it should as the lungs fill with air and oxygen from the air infuses the blood cells; the brain's synapses are firing and data of all sorts coming from both the inside of and outside the body are being processed properly--smells, sights, tastes, touches, sounds; blood pressure is 120 over 80; the exchange of nutrients and the elimination of waste products are fully functioning; in short, every system is performing optimally.
One thing is missing, however, and that is a spirit. Impossible, you say. Well, yes, but--but, if someone outside of that body I've just described were to pierce the heart of that living body in such a way that the heart stopped beating, the body would begin to die. Within minutes, it would experience brain death and the bodily systems I've just described would cease to function. The body would then begin the steady and inexorable process of decay and decomposition.
A materialist who happens to be observing the phenomenon I've just described would likely say, "Well, we've just witnessed the life/death cycle at work whereby the chemicals comprising the living body are simply rearranged and become part of other chemicals in the ongoing process of life and death--the Great Mandella (wheel of life)." In a playful mood, the materialist might even say, "The dearly departed is in the process of becoming plant food for daisies, which in turn will decay and die, providing food for other life forms."
A Christian, on the other hand, would insist that life does not end with physical death, nor does a dead body, through decomposition, simply provide fertilizer to the soil. To the Christian, physical death ushers the believer into what might be called a segue to eternal life.
Early believers and the apostle Paul referred to deceased brothers and sisters in Christ as those who had fallen asleep in Christ (see 1 Corinthians 15:18, 20, 51). This "falling asleep" was not just a euphemism, but it was a way of describing the transition from the perishable, mortal, and physical body to the imperishable, immortal, and spiritual body.
Regardless of their eschatology, most Christians believe that that transition will be completed with the return of the Lord Jesus Christ, when the dead in Christ shall rise with spiritual, heavenly bodies, like unto our Lord Jesus' body. Regardless of when that return for his own may be, we are assured that our Savior
will transform the body of our humble state into conformity with the body of His glory, by the exertion of the power that He has even to subject all things to himself (Philippians 3:21).
Or as the apostle John put it,
See how great a love the Father has bestowed on us, that we would be called children of God; and such we are. For this reason the world does not know us, because it did not know Him. Beloved, now we are children of God, and it has not appeared as yet what we will be. We know that when He appears, we will be like Him, because we will see Him just as He is” (1 John 3:1-2 NASB Updated).
In the interim between a Christian’s death and subsequent resurrection, which will occur when Christ returns for his own, the Christian’s spirit lives on and is in some way “present with the Lord,” the “proof text” of which is 2 Corinthians 5:8, which follows, along with its context:
Therefore, being always of good courage, and knowing that while we are at home in the body we are absent from the Lorde—for we walk by faith, not by sight—we are of good courage, I say, and prefer rather to be absent from the body and to be at home with the Lord. Therefore we also have as our ambition, whether at home or absent, to be pleasing to the Lord (vv.6-9).
A somewhat parallel passage is in Paul’s letter to the Philippian believers,
For to me, to live is Christ and to die is gain. But if I am to live on in the flesh, this will mean fruitful labor for me; and I do not know which to choose. But I am hard-pressed from both directions, having the desire to depart and be with Christ, for that is very much better, yet to remain on in the flesh is more necessary for your sake (1:21-24 NASB Updated, includes italics).
Besides the metaphor of sleep to describe the transition from death to resurrection, Paul also uses the metaphor of nakedness (or being unclothed) and the metaphor of a tent and a house (or dwelling):
For we know that if the earthly tent which is our house is torn down, we have a building from God, a house not made with hands, eternal in the heavens. For indeed in this house we groan, longing to be clothed with our dwelling from heaven, inasmuch as we, having put it on, will not be found naked. For indeed while we are in this tent, we groan, being burdened, because we do not want to be unclothed but to be clothed, so that what is mortal will be swallowed up by life. Now He who prepared us for this very purpose is God, who gave to us the Spirit as a pledge (2 Corinthians 5:1-5 NASB Updated, includes italics).
When we combine the teaching in all the above passages, one thing becomes very clear: In death, every believer is alive and in the presence of the Lord. As for what “form” that presence will take, the Bible does not tell us. As the apostle John, whom I’ve quoted above, says,
. . . it has not appeared as yet what we will be . . . (1 John 3:2, excerpt).
Nevertheless, we do know at least two things: 1) that to die is to be in Jesus’ presence, and 2) that to be in Jesus’ presence is to be a living spirit. That spirit may be disembodied (or unclothed), but since Christ through his resurrection is the first fruits of our resurrection (see 1 Corinthians 15:20 and 23) we are simply awaiting that day when our spirit and our glorified and sinless body will be united, which was God’s original design for his image bearers.
From that day forward we will never again be subject to death, which will be swallowed up in victory (Isaiah 25:8; 1 Corinthians 15:54), but we will live forever and "bear the image of the heavenly" Jesus (1 Corinthians 15:49), who loved us and gave himself for us.