João 13:19

From henceforth I tell you before it come to pass, that, when it is come to pass, ye may believe that I am he.

The treachery of Judas and denial of Peter were events of such negative force that Jesus moved to protect his disciples against the impact which such actions would have upon their faith. The whole terrible ordeal of the trials, crucifixion, and death, was almost upon them; and the apostles were here schooled against the very worst that could happen.

That I am he ... Jesus never lost sight of the fact which he came into the world to establish, namely, that he was God appearing in human form, entitled to human worship and adoration upon the part of all who would enter into eternal life, and himself being the source of that eternal life. Even negative events like the betrayal and denial were laid under tribute to maintain and buttress the apostles' faith, this being accomplished by the Lord's accurate prophecy of them.