Peter knew Jesus was reversing roles. He wanted to know why Jesus would want to wash his feet. After Jesus’ death and resurrection, Peter would understand why Jesus did this.
Peter said that Jesus would never wash his feet because He was not his servant. Once again, we see the thoughtless response of Peter. Note Mark 8:32; 9:5 where Peter speaks out of turn. Jesus’ response was surprising. “Unless I wash you, you have no part with Me.” Jesus meant that if He did not wash his sins away by His atoning death (Revelation 1:5), Peter would have no real relationship with Jesus. I John 1:7.
Peter continues to miss the spiritual lesson that Jesus is attempting to teach him. He is certain about his desire to be joined to Jesus. Once Peter gets it, Peter asks Jesus to wash his hands and head as well as his feet. Look at Jesus’ response. A person who has had a bathe needs only to wash his feet; his whole body is clean. A preferable interpretation of this portion of scripture would be the following:
Jesus said that not all of them were clean. Jesus was speaking of Judas Iscariot. Note John 13:11, 18. This suggests that he was not converted. Speaking more on this subject, Judas had rejected the life-giving, cleansing words of Jesus. Note John 6:63 and John 15:3. This shows that he was still in his sins. John stresses here the supernatural knowledge of Jesus concerning Judas’ deception. John states in John 2:25 and John 4:29 the knowledge of Jesus concerning man. He is able to read hearts. Remember Jesus was able to read the Samaritan woman’s heart when He met her at the well.