1 Corinthians 15:51-52

 Behold, I tell you a mystery; we shall not all sleep, but we shall all be changed, 52 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 shall be changed.

Here the rapture is spoken of as a mystery, or as something previously hidden, but now revealed—for it was never mentioned in the Old Testament and only mentioned one time in the gospels, in John 14:1-3.  The Corinthians had not heard of it before, but apparently it was revealed to Paul by the Holy Spirit.

The teaching of the rapture here is quite self-explanatory: (1) all those of the church, living and dead, at the point of the rapture will be changed, or transformed—our corruptible bodies will become incorruptible; (2) it will happen very rapidly—as fast as…