To this they received the answer, "He who has dipped his hand with Me in the dish will betray Me." Matthew alone adds that afterward Judas also asked the Lord, "Is it I, Rabbi?" and received an affirmative answer.
Finally, John says nothing about the questions each disciple put to the Lord. He relates how John, who was reclining at that time on Jesus' breast, asked the Lord at Peter's sign and received the answer, "It is he to whom I shall give this morsel when I have dipped it."
The end of this history belongs to John alone. Clearly the Evangelists relate different circumstances of the same event.
Luke, shortening the account, gives only the prediction of the betrayer and Jesus Christ's warning to him. Concerning the disciples, he gives their first confusion and their conversation with one another.
Matthew and Mark give the questions which each of them then addressed to the Lord. They also give the first indication of the betrayer, still general and unclear, together with a warning to him.
One may think that the fulfillment of this indication occurred at the same time as the indication given to John. Judas, striving either to be unconstrained and bold, or to appear so, turned to the Lord with the question, "Is it I, Rabbi?" He received the quiet answer, "Yes, you."
The disciples probably did not hear this last answer. They understood the Lord's words, "He who has dipped his hand with Me in the dish," in the most general sense. It meant, "one of the twelve," or, "the hand of him who betrays Me is with Me at the table" (Lk 22:21).
Then Peter turned to John and gave him a sign to ask Jesus who it was. If this happened during that part of the supper when the master of the house broke the bread and distributed it to those present, the revelation of Judas as the betrayer may be understood in this way.
Jesus Christ answered John, "It is he to whom I shall give this morsel when I have dipped it." This was the moment when, passing the portions of bread in order, He was to give a portion to Judas.
Judas's agitated state, and his effort to mask that state of soul, made him move his hand toward the dish too early. The Lord was still only lowering His hand into the dish with the morsel of bread intended for him.