His disciples stared at one another, at a loss to know which of them he meant.
The disciples had no idea that someone among them would betray Jesus. Even Judas had asked: “Is it I?” (Mark 14:19; Matt 26:22). Their thought was that they may sometime in the future fall short of being there for Jesus, but one of their band to deliberately betray Jesus to His enemies was beyond their perceptions, which was probably a good thing for Judas, for if they had known what he was about to do, these hot-headed Galileans would probably have killed him.
Matthew 26:22 They were very sad and began to say to him one after the other, “Surely not I, Lord?”
Obviously Judas had covered over his deeds quite well. He had been putting on an act and living a lie that deceived everyone but Jesus. By our outward actions we may deceive everyone, but we cannot hide the truth from Christ. Also, we must be careful into whose hands we trust ourselves. Wolves in sheeps clothing are not always easily discernable.