John 13:6-11

He came to Simon Peter, who said to him, "Lord, are you going to wash my feet?" Jesus replied, "You do not realize now what I am doing, but later you will understand."  "No," said Peter, "you shall never wash my feet." Jesus answered, "Unless I wash you, you have no part with me."  "Then, Lord," Simon Peter replied, "not just my feet but my hands and my head as well!" Jesus answered, "Those who have had a bath need only to wash their feet; their whole body is clean. And you are clean, though not every one of you." For he knew who was going to betray him, and that was why he said not every one was clean.

You do not realize now what I am doing, but later you will understand 
John 13:12-15  When he had finished washing their feet, he put on his clothes and returned to his place. "Do you understand what I have done for you?" he asked them. "You call me 'Teacher' and 'Lord,' and rightfully so for that is what I am. Now that I, your Lord and Teacher, have washed your feet, you also should wash one another's feet. I have set you an example that you should do as I have done for you." 

Those who have had a bath need only to wash their feet; their whole body is clean. And you are clean 
John 15:3  "You are already clean because of the word I have spoken to you."
John 17:17  "Sanctify them by the truth; your word is truth."

though not every one of you 
John 13:18  "I am not referring to all of you; I know those I have chosen. but this is to fulfill this passage of Scripture: 'He who shared my bread has turned against me.' " (Psalm 41:9)

For he knew who was going to betray him 
John 13:26-27  Jesus answered, "It is the one to whom I will give this piece of bread when I have dipped it in the dish." Then, dipping the piece of bread, he gave it to Judas, the son of Simon Iscariot. As soon as Judas took the bread, Satan entered into him. So Jesus told him, "What you are about to do, do quickly."

(parentheses are mine)

Scriptures taken from the Holy Bible, New International Version® NIV®, 
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