John 13:6-10

(6) He came to Simon Peter, who said to him, "Lord, are you going to wash my feet?" (7) Jesus replied, "You do not realize now what I am doing, but later you will understand." (8) "No," said Peter, "you shall never wash my feet." Jesus answered, "Unless I wash you, you have no part with me." (9) "Then, Lord," Simon Peter replied, "not just my feet but my hands and my head as well!" (10) Jesus answered, "A person who has had a bath needs only to wash his feet; his whole body is clean. And you are clean, though not every one of you." 

Jesus taught the apostles through this simple yet extremely humble action. Here He was, the true Son of GOD washing the feet of His followers. It was an example of ultimate humility and how we should live our lives to serve others, no matter how lofty our status.

Aside from being en example in humility, Jesus displayed an important lesson for our spirit. When we accept Jesus in to our hearts, repent, get baptised and receive the Holy Spirit, we have been cleansed. Our bodies our spiritually clean but when we walk down the road, we will slip up and get dust on our feet. Our human nature and the constant temptations of the evil one will cause us to sin occassionally but if we repent and do our best to avoid the "dust" of sin, our Lord and Savior, Jesus Christ will always be there to wash away the dust.