John Calvin on Luke 24:31

Luke 24:31. And their eyes were opened. By these words, we are taught that there was not in Christ any metamorphosis, or variety of forms, by which he might impose on the eyes of men, (as the poets feign their Proteus,) but that, on the contrary, the eyes of beholders were mistaken, because they were covered; just as, shortly afterwards, he vanished from the eyes of those very persons, not because his body was in itself invisible, but because God, by withdrawing their rigor, blunted their acuteness. Nor ought we to wonder that Christ, as soon as he was recognized, immediately disappeared; for it was not advantageous that they should any longer behold him, lest, as they were naturally too much addicted to the earth, they might desire again to bring him back to an earthly life. So far, then, as it was necessary to assure them of his resurrection, he made himself visible to them; but by the sudden departure, he taught them that they must seek him elsewhere than in the world, because the completion of the new life was his ascension to heaven.