John 13:6

Then cometh he to Simon Peter
After having washed the feet of some of the disciples, as is thought by some interpreters, and particularly the feet of Judas, without any repulse; though others are of opinion that he began with Peter, who modestly, and out of reverence to him, refuses to be washed by him:

and Peter saith unto him, Lord, dost thou wash my feet!
he speaks as one surprised and astonished that Christ should offer to do any such thing to him; that he, who was the Son of the living God, should wash the feet of such a sinful man as he was; that those hands, with which he had wrought such miracles, as the opening the eyes of the blind, cleansing lepers, and raising the dead, should be employed in washing his defiled feet, the meaner and inferior parts of his body; this he thought was greatly below his dignity and character, and too much to be done by him to such a worthless creature as he was.