We will all be changed-in a flash,at the last trumpet

I Corinthians 15:35-58
How are the dead raised? with what kind of body will they come? How foolish! What you sow does not come to life unless it dies. When you sow, you do not plant the body that will be, but just a seed, perhaps of wheat or something else.
There are also heavenly bodies and there are earthly bodies; but the splendor of the heavenly bodies is one kind, and the splendor of the earthly bodies is another.
So will it be with the resurrection of the dead. The body that is sown is perishable, it is raised imperishable; sown in dishonor, raised in glory; sown in weakness, raised in power; sown a natural body, raised a spiritual body.
If there is a natural body, there is also a spiritual body. So it is written:"The first man Adam became a living being" ; the last Adam a life giving spirit. The first man was of the dust of the earth, the second man from heaven. And just as we have borne the likeness of the earthly man, so shall we bear the likeness of the man from heaven.
We will not all sleep, but we will all be changed-- in a flash, in the twinkling of an eye, at the last trumpet.
For the perishable must clothe itself with the imperishable, and the mortal with immortality.
Let nothing move you. Always give yourselves fully to the work of the Lord, because you know that your labor in the Lord is not in vain.
Why?
Change of our body from dead to raise with splendor of heaven. Paul explained very clearly.
The old was physical, the new will be spiritual and immortal. It will as far out shine the old boy as a full-grown pant outshines the shrivelled seed from which it grows.
We can sing a victory song of praise ad thanksgiving to God.
Resurrection is a change from temporary body to spiritual body like seed be sown and grow in another body.
Clothe with the imperishable :  for we are given the mercy from the Lord and redeemed through Jesus Christ, so it comes from heaven, from outside.
The trumpet here is the same story described in revelation John wrote.
How?
Always give ourselves fully to the work of the Lord, because our labor in the Lord is not in vain. Rejoice and do what should I do for the work of the Lord.