Catena Aurea on John 13:21–30: John Chrysostom

But not even then did our Lord expose the traitor by name; Jesus answered, He it is, to whom I shall give a sop when I have dipped it. Such a mode of declaring him, should itself have turned him from his purpose. Even if a partaking of the same table did not shame him, a partaking of the same bread might have. And when He had dipped the sop, He gave it to Judas Iscariot, the son of Simon.