Chapter 13 — Part I: The Creed — Article XI: The Resurrection of the Body
Section 18. Nor does the Apostle in his Epistle to the Thessalonians dissent from this doctrine, when he says: The dead who are in Christ shall rise first, then we who are alive, who are left, shall be taken up together with them in the clouds to meet Christ, into the air. St. Ambrose explaining these words says: In that very taking up, death shall take place, as it were, in a deep sleep, and the soul, having gone forth from the body, shall instantly return. For those who are alive shall die when they are taken up that, coming to the Lord, they may receive their souls from His presence; because in His presence they cannot be dead. This opinion is supported by the authority of St. Augustine in his book On the City of God."