As Jesus is gathered with His disciples, He gets up from the table to begin to wash their feet. When gets to Peter, Peter refuses to let Jesus wash his feet. Jesus was the one who Peter promoted as the Messiah, the Son of God (even if he didn't quite understand it fully yet (Luke 24:45, etc.), there was no way He was going to wash his feet. At this point, Jesus tells Peter that if he won't let Him wash his feet, that Peter will have no part in His work (John 13:8). Peter's response (John 13:9) shows that he misunderstands verse 8 and now is asking to be completely washed. Jesus responds and lets Peter know that the washing He is administering has nothing to do with salvation, but an example of not only humility and servanthood, but the daily cleansing that each believer needs. Just as the dirt from the roads would gather on the feet of a person as they walked the city streets, even after coming from the central bath house (read more about it here) where they have been fully cleaned, sin gathers in the life of the believer and we need that daily cleansing, or repentance of sin. So, this is not only an example of humility and servanthood, but a picture of our need for daily cleansing from sin as believers.
With this in mind, when we reconsider what Jesus said to Peter, we see that Jesus warns him that unconfessed sin with keep Peter apart of the ministry and fellowship of Jesus. If we want to be A PART of the work of the Lord, we cannot allow unconfessed sin in our heart and life. Ephesians 5:25-26 give us the mode of washing today: the Word of God. It is through our daily, consistent study of the Word of God that we can be washed of the daily sin that gathers. Without this daily washing, we will not be A PART of our Lord's work, but it will keep us APART from the work.
So today, at this moment, are you APART or A PART?