This wonderful passage comes from that event we know as the last meal Jesus shared with his disciples just before the Passover.
In this act of humble service Jesus has shown the gospel in action. The disciples didn’t need their feet washed, Jesus knew that, and they knew it. The feet washing would have been done earlier in any evening event but here Jesus is telling (no, demonstrating) for his followers what following Him really requires.
An act of humble service can be many things: let’s see how we can live this gospel story today.