It will forever be a mystery as to how Judas could hang out with and be taught by Jesus for three years and then turn around and betray him. Judas should be an example to us that even the most “spiritual” people might not really be spiritual on the inside. In The Cost of Discipleship, writing about Jesus sending out the disciples in Matthew 10, Dietrich Bonhoeffer said,
No power in the world could have united these men for a common task, save the call of Jesus. But that call transcended all their previous divisions, and established a new and steadfast fellowship in Jesus. Even Judas went forth to the Christ-work, and the fact that he did so will always be a dark riddle and an awful warning (p. 205).
We need to heed the warning of Paul in 2 Corinthians 13:5 when he said, “Examine yourselves, to see whether you are in the faith. Test yourselves. Or do you not realize this about yourselves, that Jesus Christ is in you? — unless indeed you fail to meet the test!”