1 Thessalonians 5:24
He who calls you is faithful; he will surely do it.
Do what? He will come again for those who have trusted in Him! The previous chapter in this book puts it this way (verse 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.
"Asleep" here refers to those who have died, having placed faith in Jesus. Jesus pioneered the path to eternal life and demonstrated that path through His own death and resurrection. This chapter goes on to explain that all who have died, believing in the Lord Jesus, will be raised one day and joint with those who are still alive at His return. Listen to this description of Jesus' coming: (verses 16-17 of chapter 4) For the Lord himself will descend from heaven with a cry of command, with the voice of an archangel, and with the sound of the trumpet of God. And the dead in Christ will rise first. Then we who are alive, who are left, will be caught up together with them in the clouds to meet the Lord in the air, and so we will always be with the Lord. The next verse says: Therefore encourage one another with these words.
And remember: He who calls you is faithful; he will surely do it. !! (exclamation marks added)