This passage contains both encouragement and warning. The encouragement is conveyed by the way that Jesus tells his disciples that one of them is going to betray him. He shows that the betrayal will happen in fulfillment of Scripture and thus in accordance with God’s plan. The warning is conveyed by the fact that Judas was not suspected by the other disciples as a traitor, showing that it is possible to be a respected member of the community of faith without being a genuine believer.
Read John 13:18-30