1 Cor 15:50-54
50 Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption.
51 Behold, I shew 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 trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.
53 For this corruptible must put on incorruption, and this mortal must put on immortality.
54 So when this corruptible shall have put on incorruption, and this mortal shall have put on immortality, then shall be brought to pass the saying that is written, Death is swallowed up in victory.
Just read the passage mentioned (notice v.50) and put it together with (1 Thes 4:13-17). Where else do you think the scriptures teaches us other then in the air, between heaven and earth? There is a descension and a resurrection that takes place and it meets together in the air. That constitutes a gathering and at that gathering people are changed in their bodies and rewards are given based upon those things done in their body when on the earth, both of the living and the dead that are raise up. This is what (1 Cor 3:13-15) is speaking to along with (1 Cor 15:40-49). I know of no place that Jesus spoke of this when on the earth nor did any of the OT prophets. This came to the apostle Paul by revelation from Jesus Christ and given to the church and body of Christ.