The fact of the mid trib rapture can be shown in just two scriptures.
The tribulation is divided into two parts: the first 42 months are general tribulation, and the last 42 months are the great tribulation: the mark of the beast, the war against the saints, all occur in the second half.
In Luke ch. 21, Jesus describes the great tribulation. After describing those events that will occur, Jesus said:
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Luk 21:36 Watch ye therefore, and pray always, that ye may be accounted
worthy to escape all these things that shall come to pass, and to stand before the Son of man.
Jesus taught that believers will escape the events of the great tribulation, if they are worthy (lukewarm believers get left behind, too).
The fact that believers escape the great tribulation, disallows a post trib rapture, because a post trib rapture obviously does not avoid going through the great trib.
Now on to the scripture, where Paul tells us what must happen before we are gathered together to be with the Lord:
2Th 2:1 Now we beseech you, brethren, by the coming of our Lord Jesus Christ, and byour gathering together unto him,
2Th 2:2 That ye be not soon shaken in mind, or be troubled, neither by spirit, nor by word, nor by letter as from us, as that the day of Christ is at hand.
2Th 2:3 Let no man deceive you by any means:
for that day shall not come,except there come a falling away first, and that man of sin be revealed, the son of perdition;
2Th 2:4 Who opposeth and exalteth himself above all that is called God, or that is worshipped; so that he as God sitteth in the temple of God, shewing himself that he is God.
The apostle Paul wrote that we will not be gathered together to be with Jesus, until first the son of perdition reveals himself to be the antichrist beyond any doubt, by stepping into the temple and proclaiming that he is God.
This is describing the event Daniel describes as occurring in the middle of the tribulation, ( the seven weeks) when the AC steps into the temple, stops the sacrifice, and declares himself to be God.
Thus the rapture can not take place until the mid trib point in time.
When you consider the two scriptures given, you find the first passage in Luke 21 allows a mid trib rapture, but not a post trib rapture.
So now we remove the possibility of post trib rapture.
Passage two in 2 Thessalonians 2, allows for a mid trib or post trib rapture, but not pre trib.
So now we remove the possibility of the pre trib rapture.
The only event allowed by both scriptures, is the mid trib rapture.
Ergo, with only two Bible passages, the mid trib rapture has been proved.
There are more scriptures for the mid trib rapture.