1 Thessalonians 4:15

"For this we say unto you by the word of the Lord, that we that are alive, that are left unto the coming of the Lord, shall in nowise precede them that are fallen asleep." Speaking concerning the faithful, and them "which are fallen asleep in Christ" (1 Cor. xv. 18); and again, "the dead shall rise in Christ." Since his discourse is not concerning the Resurrection only, but both concerning the Resurrection and concerning the honor in glory; all then shall partake of a Resurrection, he says, but not all shall be in glory, only those in Christ. Since therefore he wishes to comfort them, he comforts them not with this only, but also with the abundant honor, and with its speedy arrival, since they knew that. For in proof that he wishes to comfort them with the honor, as he goes on, he says, "And we shall be ever with the Lord": and "we shall be caught up in the clouds." But how do the faithful fall asleep in Jesus? It means having Christ within themselves. But the expression, "He shall bring with Him," shows that they are brought from many places. "This." Something strange he was about to tell them. On this account he also adds what makes it worthy of credit; "From the word of the Lord," he says, that is, we speak not of ourselves, but having learnt from Christ, "That we that are alive, that are left unto the coming of the Lord, shall in nowise precede them that are fallen asleep." Which also he says in his Epistle to the Corinthians; "In a moment, in the twinkling of an eye." (1 Cor. xv. 52) Here he gives a credibility to the Resurrection by the manner also in which it will occur. For because the matter seems to be difficult he says that as it is easy for the living to be taken up, so also for the departed. But in saying "we," he does not speak of himself, for he was not about to remain until the Resurrection, but he speaks of the faithful. On this account he has added, "We that are left unto the coming of the Lord shall in nowise precede them that are fallen asleep." As if he had said, Think not that there is any difficulty. It is God that does it. They who are then alive shall not anticipate those who are dissolved, who are rotted, who have been dead ten thousand years. But as it is easy to bring those who are entire, so is it also those who are dissolved.

And sayest thou, How is it possible for one that is man not to mourn?… Say not then, "He is perished and shall no more be;" for these be the words of unbelievers; but say, "He sleepeth and will rise again," "He is gone a journey and will return with the King." Who sayeth this? He that hath Christ speaking in him. "For," saith he, "if we believe that Jesus died and rose again" and revived, "even so them also which sleep in Jesus will God bring with Him." If then thou seek thy son, there seek him where the King is, where is the army of the Angels; not in the grave; not in the earth; lest whilst he is so highly exalted, thyself remain grovelling on the ground.