Now it followed from all the predictions which were uttered regarding Him— among which was this prediction of the resurrection— and, from all that was done by Him, and from all the events which befell Him, that this event should be marvellous above all others. For it had been said beforehand by the prophet in the person of Jesus: “My flesh shall rest in hope, and You will not leave my soul in Hades, and will not suffer Your Holy One to see corruption.” And truly, after His resurrection, He existed in a body intermediate, as it were, between the grossness of that which He had before His sufferings, and the appearance of a soul uncovered by such a body.
And hence it was, that when His disciples were together, and Thomas with them, there “came Jesus, the doors being shut, and stood in the midst, and said, Peace be unto you. Then says He to Thomas, Reach hither your finger,” etc. And in the Gospel of Luke also, while Simon and Cleopas were conversing with each other respecting all that had happened to them, Jesus “drew near, and went with them. And their eyes were holden, that they should not know Him. And He said unto them, What manner of communications are these that you have one to another, as you walk?”
And when their eyes were opened, and they knew Him, then the Scripture says, in express words, “And He vanished out of their sight.” And although Celsus may wish to place what is told of Jesus, and of those who saw Him after His resurrection, on the same level with imaginary appearances of a different kind, and those who have invented such, yet to those who institute a candid and intelligent examination, the events will appear only the more miraculous.
Source: Against Celsus (New Advent)