ISB ~ 1 Thessalonians 4 v13

asleep:A metaphor for death. In Scripture, the expression hints that death is only a temporary state that will end when the righteous are awakened at the resurrection (Is 26:19; Dan 12:2). The gospel tells us that death is not extinction or the end of all things, but a step closer to eternal life (CCC 1010, 1016). For the state of the soul after bodily death, see note on 2 Cor 5:8.

may not grieve:It is human to mourn the death of a loved one; it is Christian to keep our sadness from sliding down to despair. Every sorrow in life can be softened by the joyful hope that the dead will live again when Jesus returns (CCC 1001).