III. Jesus instituting the Blessed Sacrament showed mercy to the traitor Judas to the last
But Jesus, sure of His purpose and undaunted in carrying out His Father's will, fulfilled the New Testament and founded a new Passover. For while the disciples were lying down with Him at the mystic Supper, and when discussion was proceeding in the hall of Caiaphas how Christ might be put to death, He, ordaining the Sacrament of His Body and Blood, was teaching them what kind of Victim must be offered up to God, and not even from this mystery was the betrayer kept away, in order to show that he was exasperated by no personal wrong, but had determined beforehand of his own free-will upon his treachery.
For he was his own source of ruin and cause of perfidy, following the guidance of the devil and refusing to have Christ as director. And so when the Lord said, “Verily I say to you that one of you is about to betray Me,” He showed that His betrayer's conscience was well known to Him, not confounding the traitor by harsh or open rebukes, but meeting him with mild and silent warnings that he who had never been sent astray by rejection, might the easier be set right by repentance.
Why, unhappy Judas, do you not make use of so great long-suffering? Behold, the Lord spares your wicked attempts; Christ betrays you to none save yourself. Neither your name nor your person is discovered, but only the secrets of your heart are touched by the word of truth and mercy. The honour of the apostolic rank is not denied you, nor yet a share in the Sacraments. Return to your right mind; lay aside your madness and be wise. Mercy invites you, Salvation knocks at the door, Life recalls you to life.
Lo, your stainless and guiltless fellow disciples shudder at the hint of your crime, and all tremble for themselves till the author of the treachery is declared. For they are saddened not by the accusations of conscience, but by the uncertainty of man's changeableness; fearing lest what each knew against himself be less true than what the Truth Himself foresaw. But you abuse the Lord's patience in this panic of the saints, and believest that your bold front hides you. You add impudence to guilt, and art not frightened by so clear a test. And when the others refrain from the food in which the Lord had set His judgment, you do not withdraw your hand from the dish, because your mind is not turned aside from the crime.
Source: Sermons (New Advent)