Origen

(t. xxxii.) As a physician, who has many sick under his care, begins with those who want his attention most; so Christ, in washing His disciples’ feet, begins with the most unclean, and so comes at last to Peter, who needed the washing less than any: Then cometh He to Simon Peter. Peter resisted being washed, perhaps because his feet were nearly clean: And Peter said unto Him, Lord, dost Thou wash my feel?