“The dust returns to the ground it came from, and the spirit returns to God who gave it” (Ecclesiastes 12:7). At death, the human spirit goes either to Heaven or Hell. Christ depicted Lazarus and the rich man as conscious in Heaven and Hell immediately after they died (Luke 16:22-31). Jesus told the dying thief on the cross, “Today you will be with me in paradise” (Luke 23:43). The apostle Paul said that to die was to be with Christ (Philippians 1:23), and to be absent from the body was to be present with the Lord (2 Corinthians 5:8). After their deaths, martyrs are pictured in Heaven, crying out to God to bring justice on Earth (Revelation 6:9-11).
These passages make it clear that there is no such thing as “soul sleep,” or a long period of unconsciousness between life on Earth and life in Heaven. The phrase “fallen asleep” (in 1 Thessalonians 4:13 and similar passages) is a euphemism for death, describing the body’s outward appearance. The spirit’s departure from the body ends our existence on Earth. The physical part of us “sleeps” until the resurrection, while the spiritual part of us relocates to a conscious existence in Heaven (Daniel 12:2-3; 2 Corinthians 5:8). Some Old Testament passages (e.g., Ecclesiastes 9:5) address outward appearances and do not reflect the fullness of New Testament revelation concerning immediate relocation and consciousness after death.
Every reference in Revelation to human beings talking and worshiping in Heaven prior to the resurrection of the dead demonstrates that our spiritual beings are conscious, not sleeping, after death. (Nearly everyone who believes in soul sleep believes that souls are disembodied at death; it’s not clear how disembodied beings could sleep, because sleeping involves a physical body.)
For more information on the subject of Heaven, see Randy Alcorn’s book Heaven.