5 After that he poureth water into a bason, and began to wash the disciples’ feet, and to wipe them with the towel wherewith he was girded.We often think that when Peter asked Christ to wash his hands and head as well as his feet, he was motivated by his typical impetuousness and an excess of zeal to prove his devotion. This might have had a little bit to do with it, but perhaps some other considerations may have occurred to him.
6 Then cometh he to Simon Peter: and Peter saith unto him, Lord, dost thou wash my feet?
7 Jesus answered and said unto him, What I do thou knowest not now; but thou shalt know hereafter.
8 Peter saith unto him, Thou shalt never wash my feet. Jesus answered him, If I wash thee not, thou hast no part with me.
9 Simon Peter saith unto him, Lord, not my feet only, but also my hands and my head.
10 Jesus saith to him, He that is washed needeth not save to wash his feet, but is clean every whit: and ye are clean,….(John 13:5-10)
It happens that the priest’s anointing ceremony in the Law of Moses involves the anointing of a priest’s right ear, right thumb, and right big toe with holy oil to symbolize how the Holy Spirit should guide their thoughts, their deeds, and their paths. Feet, hands, head. It is possible that Peter may have had this symbolism in mind when he asked for his hands and head to be washed as well as his feet.
28 And the priest shall put of the oil that is in his hand upon the tip of the right ear of him that is to be cleansed, and upon the thumb of his right hand, and upon the great toe of his right foot, upon the place of the blood of the trespass offering:
29 And the rest of the oil that is in the priest’s hand he shall put upon the head of him that is to be cleansed, to make an atonement for him before the Lord. (Leviticus 14:28-29)
17 ¶ And the Lord spake unto Moses, saying,
18 Thou shalt also make a laver of brass, and his foot also of brass, to wash withal: and thou shalt put it between the tabernacle of the congregation and the altar, and thou shalt put water therein.
19 For Aaron and his sons shall wash their hands and their feet thereat:
20 When they go into the tabernacle of the congregation, they shall wash with water, that they die not; or when they come near to the altar to minister, to burn offering made by fire unto the Lord:
21 So they shall wash their hands and their feet, that they die not: and it shall be a statute for ever to them, even to him and to his seed throughout their generations. (Exodus 30:17-21)