Origen

“ For as no one could reasonably blame Jesus for not having admitted all His apostles to the high mountain, but only the three already mentioned, on the occasion of His transfiguration, when He was about to manifest the splendour which appeared in His garments, and the glory of Moses and Elias talking with Him, so none could reasonably object to the statements of the apostles, who introduce the appearance of Jesus after His resurrection as having been made not to all, but to those only whom He knew to have received eyes capable of seeing His resurrection. ”

“ For if we believe that Jesus died, and rose again, even so them also that sleep in Jesus will God bring with Him. For this we say unto you by the word of the Lord, that we who are alive and remain unto the coming of the Lord, shall not prevent them that are asleep. ”

“ And respecting the living the words are these, “And we shall be changed;” an expression which follows immediately after the statement, “The dead shall be raised first.” [6] Moreover, in the first Epistle to the Thessalonians, describing the same change in different words, he says, that they who sleep are not the same as those who are alive ”