The teaching of the chapter is so profound that often we neglect it's obvious conclusion: doing. Knowing and doing go hand in hand. So why don't we always do this? What we are called to do is not just washing each others feet, that would almost be acceptable. What we are called to do goes way beyond that to the point of lowering ourselves beyond our respectability in the service of people we'd really rather not lower ourselves to. I think of all the stay at home Christians that have been hurt by other Christians. Whose feet are they washing there at home? Who are they lowering themselves for? How is our Lord's example being lived in their lives? Jesus said "each other's feet". Who are we to pick and choose whose other feet we'd be willing to clean?
It may be too easy to separate this commandment out from the context from which it was delivered. We might think of love as warm fuzzy "good Sunday morning" fellowship doing charitable things for our hard pressed. The context is the giving of one's life. Peter understood this in the verses to follow but was unsure of the immediate implementation in regards to what he should be giving toward Jesus in His sacrifice.
We return to the theme of being willing to do good, having good intents, but lacking the resolve and resource to sustain such. It is only by the empowering of the Holy Spirit that such sacrifice and goodness can be made.
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