Jesus is the Lamb of God who takes away the sin of the world. He works on a much smaller scale as well.
In John 13, Jesus began to wash the disciples feet as a demonstration of His love for them. When He came to Peter’s side of the table, Peter objected and, in a sense, we understand his objection because Jesus was the Master and the Master should be the one having his feet washed; He should not be the one washing. Jesus, of course, overcame Peter’s initial refusal, and then Peter bounced to the opposite side and told Jesus to give him a full-body bath. Jesus again corrected Peter’s misunderstanding by explaining that dirty feet didn’t necessarily mean his face was filthy.
The first lesson of John 13 is about service and Jesus taught His disciples to follow His pattern of humility. But there is another issue as well, the issue of cleanliness.
We are Christians, and one of the things that means is that we are clean; our sins have been forgiven. Our body of sin has been washed in Christ. But our belief of this and our having confessed our sins for sake of salvation does not mean that it was one confession and done. We, as Christians, get our feet dirty with sin. John teaches Christians in 1 John 1 that, for the sake of our ongoing fellowship with God and with each other, we must keep on confessing our sins.
We ought to confess our sins each time we sin. And as a congregation, when we gather for sake of fellowship with God and each other, we do well to wipe our dirty feet at the door rather than track mud all over the place.