Lucas 24:16

But their eyes were holden,— St. Mark says that our Saviour appeared to the two disciples in another form, Marco 16:12. St. Luke, that their eyes were holden: who does not see that both evangelists, meant to express the same thing? If Jesus appeared in another form, their eyes of course were holden that they should not know him: all that the historians meant to intimate is, that there was an impediment which prevented their knowing him. That this might happen either in a natural way or a supernatural way, may be proved in a manner agreeable to reason and true philosophy; and such aswill correspond exactly with the expressions of both the evangelists.

To state the case in a natural way; two men meet an acquaintance whom they thought dead; they converse with him for some time, without suspecting who he is; the very persuasion they were under that he was dead, contributing greatly to their not knowing him: besides, he appeared in a habit and form different from what he used when they conversed with him; the tone of his voice might be altered; he appeared to them on a journey, and walking with them side by side, in which situation no one of the company has a full view of another: moreover, their thoughts were so swallowed up in the depth of their grief, that as they took little notice of any thing without them, so they might not narrowly examine his features: and where then was the impossibility of their not knowing him? Yet as the words may be taken so as to signify some supernatural restraint, doubtless, there might have been some particular agency from above, either to divert their minds from looking steadfastly upon him, or so to affect their memories, as to render them incapable of recollecting who he was.

Compare Génesis 21:19. Números 22:31 and 2 Reyes 6:17-18.