John Calvin on John 13:7

7. What I do. We are taught by these words, that we ought simply to obey Christ, even though we should not perceive the reason why he wishes this or that thing to be done. In a well-regulated house, one person, the head of the family, has the sole fight to say what ought to be done; and the servants are bound to employ their hands and feet in his service. That man, therefore, is too haughty, who refuses to obey the command of God, because he does not know the reason of it. But this admonition has a still more extensive meaning, and that is, that we should not take it ill to be ignorant of those things which God wishes to be hidden from us for a time; for this kind of ignorance is more learned than any other kind of knowledge, when we permit God to be wise above us.

John 13:8-11

8. Peter saith to him, Thou shalt never wash my feet. Jesus answered him, If I wash thee not, thou shalt have no part with me. 9. Simon Peter saith to him, Lord, not my feet only, but also my hands and my head. 10. Jesus saith to, him, lie who is washed needeth not to wash more than his feet, but is altogether clean; and you are clean, but not all. 11. For he knew who it was that should betray him; “Lequel c’estoit qui le trahiroit.” therefore he said, You are not all clean.