The Bible presents death as separation: physical death is the separation of the soul from the body, and spiritual death is the separation of the soul from God.
Death is the result of sin. “For the wages of sin is death,” Romans 6:23a. The whole world is subject to death, because all have sinned. “By one man sin entered the world, and death by sin, and so death passed upon all men, for that all have sinned” (Romans 5:12). In Genesis 2:17, the Lord warned Adam that the penalty for disobedience would be death—“you will surely die.” When Adam disobeyed, he experienced immediate spiritual death, which caused him to hide “from Lord God among the trees of the garden” (Genesis 3:8). Later, Adam experienced physical death (Genesis 5:5).
On the cross, Jesus also experienced physical death (Matthew 27:50). The difference is that Adam died because he was a sinner, and Jesus, who had never sinned, chose to die as a substitute for sinners (Hebrews 2:9). Jesus then showed His power over death and sin by rising from the dead on the third day (Matthew 28; Revelation 1:18). Because of Christ, death is a defeated foe. “O death, where is thy sting? O grave, where is thy victory?” (1 Corinthians 15:55; Hosea 13:14).
For the unsaved, death brings to an end the chance to accept God’s gracious offer of salvation. “It is appointed unto men once to die, but after this the judgment” (Hebrews 9:27). For the saved, death ushers us into the presence of Christ: “To be absent from the body, and to be present with the Lord” (2 Corinthians 5:8; Philippians 1:23). So real is the promise of the believer’s resurrection that the physical death of a Christian is called “sleep” (1 Corinthians 15:51; 1 Thessalonians 5:10). We look forward to that time when “there shall be no more death” (Revelation 21:4).
Recommended Resources: Heaven by Randy Alcorn and Logos Bible Software.