Judas was the disciple who betrayed Jesus. Little is known of him apart from the fact that he looked after the disciples’ money bag and was reputed to steal from it.(John 12:6).
Judas is mentioned by name in five episodes in the final week of Jesus’ life. He got angry at Jesus being anointed in Bethany (John 12:1-8); he agreed a price to betray Jesus (Matt 26: 14-16); Jesus predicted that Judas would betray him (John 13:21-30); Judas betrayed Jesus with a kiss (Matt 26:47-50); Judas killed himself (Matt 27:3-10).
The question remains why did Judas betray Jesus? The simple answer is that he did it for the money. Another theory is that he was afraid what the authorities would do to Jesus’ followers, so he tried to please them by selling Jesus to them. Another theory is that Judas had always seen Jesus as a political revolutionary but when it became obvious that Jesus’ revolution was of a different kind, Judas decided to force the issue and give Jesus a chance to declare himself to the authorities. Judas committed suicide when it all went badly wrong.
Judas was replaced by Matthias as the twelfth disciple (Acts 1:25).