From Paul Metzger
1Th 4:13 But we do not want you to be uninformed, brothers, about those who are asleep, that you may not grieve as others do who have no hope.
1Th 4:14 For since we believe that Jesus died and rose again, even so, through Jesus, God will bring with him those who have fallen asleep.
Zec 14:9 And the LORD will be king over all the earth. On that day the LORD will be one and his name one.
The passages in Zechariah and I Thessalonions both look forward to the "Coming of the Lord."
Paul advises us to not grieve, in this instance over fellow Christians who have "fallen asleep" or died, "...like other people who have no hope."
We have a glorious hope in Christ, and know that one day He will be recognized as King over all the earth, and we will be with the Lord forever.
This is our hope, and we are to encourage and comfort one another with these words.