The misleaders at Thessalonica were not so infatuated as to imagine that the Lord had come, and by His presence gathered to Himself on high all the saints, whether departed, or alive and waiting for Him. Even they never dreamt that He had descended into the air, and translated all the once suffering children of God to be with Him glorified in heaven. Since it was patent to all eyes that the saints in Thessalonica, and their brethren throughout the world, were still on earth, they could hold no such suicidal thought as that the deceased saints were already raised from their graves, and themselves were left behind. The truth is that they were not thinking about the Lord's presence: their delusion was not on this score at all, but about "the day of the Lord," as verse 2 makes clear and indisputable. They did conceive that His "day" was not merely "at hand," which is true, but "present," which is false. Identify "the coming" with "the day" of the Lord, and all is confusion; distinguishing between them, you forthwith receive light, and need put no strain on the words, which are instructive in proportion to the discernment of their exact force.
Now it is very intelligible that a misleader might avail himself of the germinant or partial application of the prophecies in ancient times to affirm that the sore troubles and persecution the Thessalonians then endured along with external distress and political convulsion, etc., indicated that day. It was not indeed Christ's presence, nor were the saints translated to heaven, which twofold event could not of course be pretended in any way to have taken place; for it is here pleaded as a self-evident guard against the error in circulation, that the day of the Lord's dealing with the living on earth had begun, and that the saints were involved in its terrors. So far in fact were any from so egregious a fancy as that Christ had come, that beyond controversy the apostle could entreat them by* (or, for the sake of) His presence and our gathering together unto Him, that they should not credit the alarming rumour that His day was there. That is, every believer in his senses was fully aware that Christ had not come, but was in heaven still, and that the saints were as yet on earth instead of being caught up to Him above. Therefore the apostle does make this a ground of appeal why they should not receive the mischievous report, no matter how strongly in appearance commended, that His day had actually dawned. Christ's presence and our gathering unto Him on high must precede that day. That on the one hand so great a joy, so bright a hope, was not the actual portion of the saints and that on the other (while Christ was still absent; they themselves and their brethren were as yet on earth, were obvious facts and irrefragable reasons why the day could not be come. The saints are to appear from heaven following Christ to bring in that day, See Revelation 17:14; Revelation 19:14. In order to this they must be translated there previously; and so we see them symbolised as in heaven from Rev. 4 and onward.