And he said unto them, It is one of the twelve, he that dippeth with me in the dish. St. Mark here uses the present participle ( ὁ ἐμβαπτόμενος), bringing the action close to the time when he was speaking.
St. Matthew (Matthew 26:23) has ( ὁ ἐμβάψας) "he that dipped his hand," using the aorist form. St. Mark's form is the more graphic. The dish probably contained a sauce called charoseth, into which they dipped their food before eating it.
The following appears to have been the order of the events:—First, our Lord, before he instituted the Holy Sacrament of the Eucharist, foretold that he would be betrayed by one of his disciples but only in general terms.
Then came the eager question from them, "Is it I?" Then Christ answered that the traitor was he who should dip his hand together with him in the dish. But this did not bring it home to the individual, because several who sat near to him were able to dip with him in the dish.
So that our Lord had as yet only obscurely and indefinitely pointed out the traitor. Then he proceeded to institute "the Lord's Supper;" after which he again intimated (Luke 22:21) that "the hand of him that betrayed him was with him on the table."
Upon this. St. Peter hinted to St. John, who was "reclining in Jesus' besom," that he should ask him to say definitely and by name who it was that should betray him. Our Lord then said to St. John, "He it is, for whom I shall dip the sop, and give it him" (John 13:26).
Our Lord then dipped the sop, and gave it to Judas Iscariot. Then it was that our Lord said to Judas, "That thou doest, do quickly" ( ὅ ποιεῖς ποίησον τάχιον) (John 13:27). Then Judas went straightway to the house of Caiaphas, and procured the band of men and officers for the completion of his horrible design.