John 13:11 - Ellicott's Commentary On The Whole Bible

For he knew who should betray him. — Comp. John 18:2, and Note on Matthew 26:48. This is the first reference to the betrayal during the feast. The words are words of warning, spoken in the love which even then might have redeemed and cleansed the heart, if it had been open to receive it. The feet of Judas were washed by his Master. Had he learnt the lesson of humility and love, he might have conquered the foul spirit of ambition and covetousness which was carrying him to destruction.