For the Lord himself will descend from heaven with a shout, with the voice of the archangel, and with God's trumpet. The dead in Christ will rise first,
Dead -- rise --  the spirits’ dead bodies will be resurrected (before we ascend, v. 17 “caught up”) so there is a “reunion” of the dead spirits with a new resurrected body. (For a description of that resurrected body see 1 Corinthians 15:42-50.)