Peter was shocked that his Lord would do a servant's job for him. Barnes notes that "Every word here is emphatic": the Lord, washing my feet. He calls it "an expression of Peter's humility, of his reverence for Jesus, and also a refusal to allow him to do it." Gill says Peter "speaks as one surprised and astonished that Christ should offer to do any such thing to him," thinking it too much to be done to "such a worthless creature as he was." The question is wonder and protest at once.

Jesus answered, "What I do thou knowest not now; but thou shalt know hereafter" (John 13:7). Peter refused: "Thou shalt never wash my feet." Jesus replied, "If I wash thee not, thou hast no part with me" (John 13:8). Then Peter swung the other way: "Lord, not my feet only, but also my hands and my head" (John 13:9). Jesus told him that one who is washed "needeth not save to wash his feet, but is clean every whit" (John 13:10).

Barnes explains that "It was uniformly the office of a servant to wash the feet of guests." Barnes adds that it was a necessity where people traveled without shoes and reclined on couches at meals. It was a common need, but a lowly task. In the Greek, the words "thou" and "my" stand side by side (su mou), setting Jesus and Peter in sharp contrast. Barnes says the act was "a symbolical action, inculcating a lesson of humility." John frames it with Jesus' full knowledge "that the Father had given all things into his hands, and that he was come from God, and went to God" (John 13:3).

Peter's question asks how the Lord could stoop so low. John's answer is that Jesus stooped because He knew exactly who He was (John 13:3). His humility was not a loss of glory but a display of it, and of love: "having loved his own which were in the world, he loved them unto the end" (John 13:1).

Jesus' reply also points beyond the basin. "If I wash thee not, thou hast no part with me" (John 13:8). To belong to Christ, a person must let Him do the cleansing. Matthew Henry writes, "It is not humility, but unbelief, to put away the offers of the gospel, as if too rich to be made to us, or too good news to be true." Peter's struggle was not that he thought too little of Jesus, but that he did not yet understand what Jesus had come to do.