Theophylact of Ohrid

The Father having given up all things into His hands, i. e. having given up to Him the salvation of the faithful, He deemed it right to shew them all things that pertained to their salvation; and gave them a lesson of humility, by washing His disciples’ feet. Though knowing that He was from God, and went to God, He thought it in no way took from His glory, to wash His disciples’ feet; thus proving that He did not usurp His greatness. For usurpers do not condescend, for fear of losing what they have irregularly got.