John 14:1-3 “Do not let your heart be troubled; believe in God, believe also in Me. In My Father’s house are many dwelling places; if it were not so, I would have told you; for I go to prepare a place for you. If I go and prepare a place for you, I will come again and receive you to Myself, that where I am, there you may be also.I Thess 4:13-18 13 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. 14 For if we believe that Jesus died and rose again, even so God will bring with Him those who have fallen asleep in Jesus. 15 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. 16 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. 17 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.
II Thess 2:1-6 Now we request you, brethren, with regard to the coming of our Lord Jesus Christ and our gathering together to Him, 2 that you not be quickly shaken from your composure or be disturbed either by a spirit or a message or a letter as if from us, to the effect that the day of the Lord has come. 3 Let no one in any way deceive you, for it will not come unless the apostasy comes first, and the man of lawlessness is revealed, the son of destruction, 4 who opposes and exalts himself above every so-called god or object of worship, so that he takes his seat in the temple of God, displaying himself as being God. 5 Do you not remember that while I was still with you, I was telling you these things? 6 And you know what restrains him now, so that in his time he will be revealed.
I Cor 15:51-53 Behold, I tell you a mystery; we will not all sleep, but we will all be changed, in a moment, in the twinkling of an eye, at the last trumpet; for the trumpet will sound, and the dead will be raised imperishable, and we will be changed. For this perishable must put on the imperishable, and this mortal must put on immortality.
when Paul write behold I show you a mystery, he is introducing something not spoken of before in scripture, something most likely revealed to him directly from The Lord.
We were told by Jesus to watch, as in watch for me because I will not give you a warning sign, I will just appear and you better be ready. That is the doctrine of immanency, that the Lord can return at any moment to take away the Bride of Christ and start the Tribulation years spoken of in Daniel 9 as the seventieth week for Israel.
Where Paul speaks to the Thessalonian believers of the ‘last Trump’ he is referring to Septuagint passages he used to teach them about the Passover and the feast of Israel/God’s Times. It is these feasts which featured trump blasts. There is a fest of trumpets featuring 100 soundings and the last is for as long as the trumpeter can use their largest inhalation. But there are other trumpets used in the feasts. Would anyone like to guess which Feast Paul might have been referring them to as being a foreshadowing of the Rapture?