The Catechism in Questions & Answers

542. Who are the “dead in Christ”?

In 1 Thessalonians 4: 16 we read of the “dead in Christ”. These are departed individuals who have been reborn out of water and the Holy Spirit, and who have allowed themselves to be prepared for the return of Christ. They belong to the congregation of the Lord and find themselves in a condition of righteousness before God, which is attained through grace and faith.

The rebirth out of water and the Spirit: see Questions 528. et seq.

“But the souls of the righteous are in the hand of God, and there shall no torment touch them. In the sight of the unwise they seemed to die: and their departure is taken for misery. And their going from us to be utter destruction: but they are in peace.”
Wisdom of Solomon 3: 1-3