The Bible does not give a large number of details concerning what happens right after we die. It is certainly safe to say that we will enter a reality that is far beyond anything we could imagine. There are also at least five concrete things the Bible does say about what we should expect at the moment of death and beyond.
First, believers will be taken into the presence of Christ in heaven. Christ is in heaven now (Acts 1:2; 3:21; 1 Thes 1:10; 4:16; 2 Thes 1:7), and believers will go to be with Him. Jesus said to the thief on the cross, "Truly I say to you, today you shall be with me in Paradise" (Luke 23:43). And on two different occasions Paul spoke of death as ushering us into the presence of Christ:
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. (Philippians 1:23-24)
Therefore, being always of good courage, and knowing that while we are at home in the body we are absent from the Lord--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 Him. (2 Corinthians 5:6-9)
Second, heaven is a place of resplendent glory, and being with Christ in the glory of heaven will be far superior to our present earthly lives. Notice that in the passages just listed, Paul says that departing this life to be with Christ "is very much better" (Philippians 1:23) and that he would "prefer rather to be absent from the body and to be at home with the Lord" (2 Corinthians 5:8). Notice also that being in heaven with the Lord is referred to as being "at home." One of the things that will make heaven so great is that we will finally feel that we are in our true home.
Third, when in heaven we will be continue looking forward (as we should be already in this life) to the resurrection of our bodies from the dead. Disembodied existence is not God's ultimate and final and greatest purpose for us. As great as it will be to be in heaven after we die, God has something greater in store: being resurrected from the dead so that we will live soul and body forever in the new heavens and new earth. While still alive, Paul stated that he was waiting eagerly for the redemption of his body (Romans 8:23). This eager anticipation for our resurrection stops not when we die, but when we finally receive the fulfillment of our anticipation in the resurrection of our bodies. Understanding this should greatly increase our desire for the full coming of God's kingdom. Piper notes:
It seems to me that the hope of resurrection does not have the same place of power and centrality for us today that it had for the early Christians. And I think one of the reasons for that is that we have a wrong view of the age to come. When we talk about the future and the eternal state we tend to talk about heaven, and heaven tends to imply a place far away characterized by non-material, ethereal, disembodied spirits.
In other words, we tend to assume that the condition that the departed saints are in now without their bodies is the way it will always be. And we have encouraged ourselves so much with how good it is for them now, we tend to forget that it is an imperfect state and not the way it will be, nor the way Paul wanted it to be for himself. Yes to die is gain, and yes, to be absent from the body is to be at home with the Lord, but no this is not our ultimate hope. This is not the final state of our joy. This is not our final or main comfort when we have lost loved ones who believe. (Piper, "What Happens When You Die? The Dead Will be Raised Imperishable")
Fourth, at the moment of death believers will be made perfect and cleansed from all sin. This follows from the above point that believers are taken to heaven immediately at death. Heaven is fully pure and free from all tarnish and sin, and therefore when God takes us to heaven He makes us fit for the experience of it by making our hearts perfect in holiness. This accords with His purpose to make us completely like Christ (Romans 8:29) and, at the return of Christ, to present us to Himself without spot or wrinkle or sin (1 Thessalonians 5:23; Ephesians 5:27).
Fifth, those who did not trust Christ in this life will be separated from God and enter a reality completely devoid of His common grace and blessing. In the parable of the rich man and Lazarus, Jesus speaks of Lazarus as being taken to heaven when he dies but the rich man, because he did not heed the Scriptures, immediately entering into great torment and being excluded from the blessing of heaven (Luke 16:22-26). Scripture speaks often of the painful reality that awaits those who do not place their faith in Christ to be rescued from sin (Matthew 13:30; 25:41; Luke 12:5; John 3:36; Romans 2:8-9; Hebrews 10:29).
Finally, we see from all these things that death is not the end of our existence. We have bodies and souls. Death is the separation of body and soul, not the end of our personhood. When we die our bodies become lifeless and are no longer the place where we "reside," but we continue to exist as souls, either with Christ in glory or separated from Christ in shame.
Knowing that death ushers us directly into the realities of either heaven or hell should make us look up to Christ as our refuge and salvation and should make us strive, as Paul, to "have as our ambition, whether at home or absent, to be pleasing to him" (2 Corinthians 5:9). Even for believers, the prospect of death is sometimes a fearful thing because death is enshrouded in great mystery as the realm to which we have never gone. But we may take courage and lay aside our fears in the confidence that we have a God who time after time says to his people, "Do not be afraid" (Joshua 11:6; Isaiah 44:8; Matthew 14:27; 17:7; 28:10; Revelation 1:17). God wants His people to be comforted in the face of death: "Do not fear, for I have redeemed you; I have called you by name; you are Mine! When you pass through the waters, I will be with you; And through the rivers, they will not overflow you. When you walk through the fire, you will not be scorched, Nor will the flame burn you" (Isaiah 43:1-2).
John Piper's sermon series, "What Happens When You Die?"
Wayne Grudem, Systematic Theology, chapter 41, "Death and the Intermediate State"