But no one at the table knew why Jesus had said this to him.
THE TRAITOR INDICATED--HE LEAVES THE SUPPER ROOM. (Joh 13:21-30) When Jesus had thus said, he was troubled in spirit, and testified, and said, Verily, verily, I say unto you, One of you shall betray me--The announcement of Joh 13:18 seems not to have been plain enough to be quite apprehended, save by the traitor himself. He will therefore speak it out in terms not to be misunderstood.
Commenting on John 13:21-30
no man . . . knew for what intent he spake this unto him . . . some thought . . . Jesus . . . said . . . But what we need . . . or, . . . give . . . to the poor--a very important statement, as showing how carefully. Jesus had kept the secret, and Judas his hypocrisy, to the last.
28. Not one of those who were at table. Either John had not yet related to others what Christ had told him, or they were so much struck by it, that they lost their presence of mind; and, indeed, ill is probable, that John himself was almost out of his senses.