Augustine of Hippo
Catena Aurea · Johannesevangelium 13
When Jesus had thus said, he was troubled in spirit, and testified, and said, Verily, verily, I say unto you, that one of you shall betray me. Then the disciples looked one on another, doubting of whom he spake. Now there was leaning on Jesus’ bosom one of his disciples, whom Jesus loved. Simon Peter therefore beckoned to him, that he should ask who it should be of whom he spake. He then lying on Jesus’ breast saith unto him, Lord, who is it? Jesus answered, He it is, to whom I shall give a sop, when I have dipped it. And when he had dipped the sop, he gave it to Judas Iscariot, the son of Simon. And after the sop Satan entered into him. Then said Jesus unto him, That thou doest, do quickly. Now no man at the table knew for what intent he spake this unto him. For some of them thought, because Judas had the bag, that Jesus had said unto him, Buy those things that we have need of against the feast; or, that he should give something to the poor. He then having received the sop went immediately out: and it was night. He then lying on Jesus’ breast, saith unto Him, Lord, who is it?
(Tr. lxii. 3) Not as some careless readers think, that then Judas received singly Christ’s body. For our Lord had already distributed the sacraments of His body and blood to all of them, while Judas was there, as Luke relates; and after this He dipped the sop, as John relates, and gave it to the traitor; the dipping of the bread perhaps signifying the deep dye of his sin; for some dipping cannot be washed out again; i. e. when things are dipped, in order to receive a permanent dye. If however this dipping meant any thing good, he was ungrateful for it, and deserved the damnation which followed him; And after the sop, Satan entered into him.