What happens to believers who have already died if Christ was not raised?
If Christ was not raised, believers who have already died—those fallen asleep in Christ—are just as doomed as anyone else. Without resurrection power there is no eternal life, so their faith would be vain and they would yet be in their sin.
Les explains that in verse 17, if Christ be not raised and stayed in the tomb, then faith is vain, all for nothing, and a person is yet in sin and doomed. The next verse applies this to believers who are “fallen asleep in Christ”—believers who had embraced Christianity, who had embraced Paul’s gospel. If there was no resurrection, they too are just as doomed as anybody else, because without resurrection power there is no eternal life; it cannot be. Les ties this back to the threefold aspect of the gospel: the eternal Creator God Himself took on human flesh, died, shed His blood, and was buried three days and three nights in the grave as proof positive that He was really dead. He notes that liberal and modernistic preachers may say that if He did raise, then He was not really dead, only unconscious and brought back to life, but no—He was literally, physically dead, and God raised Him from the dead the third day according to the Scriptures. Verse 19 adds that if in this life only we have hope in Christ, we are of all men most miserable.
Then they also which are fallen asleep in Christ are perished.