He humbled Himself

…Rose from supper. He laid aside his outer garments, and taking a towel, tied it around his waist. Then he poured water into a basin and began to wash the disciples' feet and to wipe them with the towel that was wrapped around him. (John 13:4-5)

 It seems likely that the disciples had been silent while Jesus was washing their feet. It was only when He came to Peter that words were spoken. In a sense, Peter was speaking for all of the disciples, as he considered it inappropriate for the one whom he had earlier called the Holy One of God to wash his feet.
 Bible commentators raise the question of whether Jesus specifically meant that believers should literally wash the feet of other believers. It seems the consensus of most commentators is that foot washing was meant as an example rather than a specific command.
 The point Jesus made seems to be that if He, as their Lord, humbled Himself by assuming the role of a servant, His disciples ought to be willing to do the same. Rather than instructing them in the particular act of washing another’s feet, Jesus was demonstrating an attitude of humility and service to others.
 He set the example of how we, as Christians, should serve others, even if it is unpleasant or humbling. —P. Amsterdam [1]

 Foot washing is not just a physical act, but a spiritual one as well. It symbolizes the spiritual purification and reconciliation offered through Jesus’ sacrifice. —Author unknown

[1] P. Amsterdam D.C. Washing the Disciples' Feet