Verse 23 - And they began to inquire among themselves, which of them it was that should do this thing. That all the disciples, on hearing this statement of their Master, should at once question their own hearts with the "Is it I?" (of St. Matthew's Gospel), shows with what cunning skill the arch-traitor must have concealed not merely his plans but his very sentiments. No suspicion on their parts ever seems to have fallen on Judas, their companion for so long a time. The direct colloquy of the Lord with the traitor, reported at length in the other Gospels on the occasion of dipping the sop into one of the Paschal dishes, was most probably carried on in a whisper (see John 13:26-29, where mention is specially made of the disciples' ignorance of the dread meaning of their Master's words to Judas).

22:21-38 How unbecoming is the worldly ambition of being the greatest, to the character of a follower of Jesus, who took upon him the form of a servant, and humbled himself to the death of the cross! In the way to eternal happiness, we must expect to be assaulted and sifted by Satan. If he cannot destroy, he will try to disgrace or distress us. Nothing more certainly forebodes a fall, in a professed follower of Christ, than self-confidence, with disregard to warnings, and contempt of danger. Unless we watch and pray always, we may be drawn in the course of the day into those sins which we were in the morning most resolved against. If believers were left to themselves, they would fall; but they are kept by the power of God, and the prayer of Christ. Our Lord gave notice of a very great change of circumstances now approaching. The disciples must not expect that their friends would be kind to them as they had been. Therefore, he that has a purse, let him take it, for he may need it. They must now expect that their enemies would be more fierce than they had been, and they would need weapons. At the time the apostles understood Christ to mean real weapons, but he spake only of the weapons of the spiritual warfare. The sword of the Spirit is the sword with which the disciples of Christ must furnish themselves.And they began to inquire among themselves,.... Two days before, at the supper in Bethany, when the same thing was hinted to them, they looked at one another, John 13:22 as persons in the utmost surprise and consternation, not being able, for a while, either to speak to Christ, or one another; but now they inquired among themselves, and of Christ likewise, Matthew 26:21

which of them it was that should do this thing; so barbarous, shocking, and horrible.