Keener provides helpful annotations and insight regarding the custom of foot washing in his IVP commentary of the New Testament. It was equally surprising to me that he had not mentioned that there were no other references, specifically with regard to foot washing in any of the Synoptic Gospels, the book of Acts or any of the epistle letters. John is the only Gospel writer that provides such a perspective on this act of hospitality, but none of the other three writers mentions it at all.
Too often, when I have read this passage of Scripture, I failed to look more deeply into the meaning of this action, or to see where else it may have occurred in the Old Testament for explanation in the New Testament. Keener points out that Abraham’s guests in Genesis 18:4 had their feet washed as he considered himself a servant to his Lord who had now visited him. He further adds that the act of washing the feet of a guest was the responsibility of a servant and not for the host, though Abraham was the host for these three guests.
Keener’s additional insight, illustrates the act of washing the feet of a guest was the duty of a servant of the household, as the lowliest of services to offer comforting refreshment to the feet of those whom had been travelling. Was this practice only for guests, or was it a daily practice within the household too?
When reading this passage of Jesus washing the feet of His disciples, the reader does not realize that this is always performed by a servant of the household, yet Jesus is the one washing the feet of His disciples, acting as a servant, “just as the Son of Man did not come to be served, but to serve,” (Matthew 20:28, also Mark 10:45). The disciples knew well that what Jesus was doing was contrary to whom He said he was/is. How could the Messiah, the one whom everyone would bow down to and worship as King, be the one whom would be willing to wash the feet of those whom He was with?
Peter had objected to Jesus washing his feet since he knew this was the responsibility of a servant saying, “You shall never wash my feet!” (13:8). He was insistent that the Son of God should have no part in performing such a lowly act of service upon him, but Peter did not realize that Jesus was doing this for more spiritual reasons than physical or sanitary reasons. Since the time the Passover was taking place, it is likely they had washed themselves completely as it was customary for them to do so, hence, Peter’s follow up request to have his entire body washed by Jesus.
Description: Julius Schnorr von Carolsfeld's (1794-1872) depiction of Jesus washing his disciples feet; Judas Iscariot is depicted in the back without a halo. Pitts Theology Library Digital Image Archive.
This was a symbolic point of reference for Peter and the others, to remember that building the kingdom of God is an act of humility and service to those whom are being served. Pride and condescension were the things that many of the Pharisees boasted about concerning themselves, but Jesus demonstrates that such an attitude and behavior is not the way to build His kingdom.
At the conclusion of Jesus washing the feet of His disciples, He asks them if they understand what He has just done for them. Jesus informed them that the one who serves his master is not greater than his master and neither was, “he who is sent greater than he who sent him.” (13:6). Because they had been with Christ and had followed Him for three years did not make them better than anyone else, but they were to be as humble with others as Jesus was to them and His act of washing their feet was a reminder of how much of a servant of Christ they must be to others. Humility and service are essential to build the kingdom of God.
It is intriguing to notice that neither Matthew, Mark nor Luke provide any accounts at all regarding this act of service in their Gospel, as John did in his Gospel. Yet in Matthew, Mark and Luke, each of these Gospels do provide an account of the last supper, but there is no mention at all regarding Jesus washing the feet of the disciples in these three Gospels, only in John.
 Albert Barnes’ Notes on the Bible in e-Sword [Bible software], Version 8.0.5, Copyright 2000-2008.
 International Standard Bible Encyclopedia in e-Sword [Bible software], Version 8.0.5, Copyright 2000-2008.
Textbook: The IVP Bible Background Commentary: New Testament by Craig S. Keener.