While the Bible speaks often of death, one death in particular, the “second death,” mankind knows little of. The phrase “second death” is found only in the book of Revelation, the first time in the letter to the church at Smyrna: “He who overcomes shall not be hurt by the second death” (Revelation 2:11).
This verse does not tell us much about the second death, only that the way to avoid it is to overcome faithfully. Revelation 20:6 provides a little more detail: “Blessed and holy ishe who has part in the first resurrection. Over such the second death has no power, but they shall be priests of God and of Christ, and shall reign with Him a thousand years.”
Just as overcomers will not be hurt by the second death, the same holds true for those who rise in the first resurrection. Popular Christianity maintains that the soul departs to its destination immediately after death, but the Bible teaches that nothing happens until or unless a resurrection occurs. In the grave there is no thought, no consciousness, and unless God resurrects someone by placing his or her spirit into another living body, that is the end of the story (see Ecclesiastes 3:19-20; 9:2-5, 10; Psalm 146:4).
The first resurrection, one to immortality for those in Christ (see I Corinthians 15:50-54; I Thessalonians 4:13-17), occurs at His return. It is also the “better resurrection” for which the heroes of faith qualified because they did not accept deliverance (Hebrews 11:35). Those in the first resurrection are raised with incorruptible, spirit bodies. These saints have been given immortality by God—there is no longer any fear of death; it is swallowed up in victory.
— David C. Grabbe