John Calvin Commentary 1 Thessalonians 4:14

"For if we believe that Jesus died and rose again, even so them also that are fallen asleep in Jesus will God bring with him." — 1 Thessalonians 4:14 (ASV)

For if we believe. He assumes this axiom of our faith: that Christ was raised up from the dead so that we might be partakers of the same resurrection; from this, he infers that we shall live with him eternally. This doctrine, however, as has been stated in 1 Corinthians 15:13, depends on another principle—that it was not for himself, but for us that Christ died and rose again. Therefore, those who have doubts about the resurrection do great injury to Christ; indeed, they, in a manner, draw him down from heaven, as is said in Romans 10:6.

To sleep in Christ, is to retain in death the connection that we have with Christ; for those who are by faith ingrafted into Christ have death in common with him, so that they may be partakers with him of life. It is asked, however, whether unbelievers will not also rise again, for Paul does not affirm that there will be a resurrection, except in the case of Christ’s members. I answer that Paul here only touches upon what suited his present design. For he did not intend to terrify the wicked, but to correct the immoderate grief of the pious and to cure it, as he does, by the medicine of consolation.