"But we do not want you to be uninformed, brethren, about those who are asleep, so that you will not grieve as do the rest who have no hope. For if we believe that Jesus died and rose again, even so God will bring with Him those who have fallen asleep in Jesus. For this we say to you by the word of the Lord, that we who are alive and remain until the coming of the Lord, will not precede those who have fallen asleep. For the Lord Himself will descend from heaven with a shout, with the voice of the archangel and with the trumpet of God, and the dead in Christ will rise first. Then we who are alive and remain will be caught up together with them in the clouds to meet the Lord in the air, and so we shall always be with the Lord. Therefore comfort one another with these words." (1st Thessalonians 4:13-18)For many people today, the idea of a resurrection to live is common place, even if they don't believe in such a resurrected life. However, in the Greek/Roman world that Paul lived in, such was not the case. Very little of their religion and mythology dealt with the idea of an after life and, if it did, it was usually in the form of a reincarnation, either to a better life for the good or a worse life for the evil. Yet for many, death was still the final exit; the door to a non-existence. For many, death became fearful; fearful for the nothingness that awaited them or fear for the possible reversal of fortunes that awaited them in reincarnation. This fear held men and women in slavery; either to appease the gods for long life or for a better existence in another life. Their future, or non-future, depended on the gods and they were held in slavery to them to do their bidding.
However, Jesus came to free us from such fear and slavery, "Therefore, since the children share in flesh and blood, He Himself likewise also partook of the same, that through death He might render powerless him who had the power of death, that is, the devil, and might free those who through fear of death were subject to slavery all their lives." (Hebrews 2:14-15) and to announce to us the resurrection from the dead, "but now has been revealed by the appearing of our Savior Christ Jesus, who abolished death and brought life and immortality to light through the gospel." (2nd Timothy 1:10) For the people of Paul's day, this was ground breaking truth and a welcome relief from their fear of death.
One day, death will be abolished. "For He must reign until He has put all His enemies under His feet. The last enemy that will be abolished is death." (1 Corinthians 15:25-26) In the end, life will be eternal and death will be no more. "and He will wipe away every tear from their eyes; and there will no longer be any death; there will no longer be any mourning, or crying, or pain; the first things have passed away." (Revelation 21:4) However, presently, death is still a reality and often the greatest pain of death is the pain of our loss. It is for the loss of those we love that we grieve. However, Paul wanted the Thessalonians to know that, even though we grieve over the loss of our loved ones, we need not grieve like others, for in our grieving we have hope. We are not like the unbelieving world, being unaware of the resurrection, but we believe that life is eternal and that one day we shall be reunited with those we have lost. I have had two friends who both lost spouses very early in life and for both of them their greatest comfort was knowing that one day they would be reunited with them in the resurrection; one day they would see them again and in that day death would no longer be able to separate them. Yes we grieve, but we grieve in hope. What tremendous comfort we can find in this truth.