The "maundy" in Maundy Thursday comes from the Latin mandatum, "commandment." The reference is to Jesus's words to his disciples after the last supper, his washing of his disciples' feet, and the departure of the betrayer Judas Iscariot. He said, "a new commandment I give you -- that you love one another. Just as I have loved you, you are to love one another."
Generally commands don't permit questions, but this command invites, even begs, this one: how exactly is it a new command? Hadn't the disciples heard Moses's command, "love your neighbor as yourself"? Narrator John doesn't leave us hanging, but works the answer into his skillfully woven account of Jesus's table- and walk-talk. John has already recounted Jesus's foot-washing and his charge, "if I, your Lord and teacher, have washed your feet, you ought to wash one another's feet." Foot-washing was a slave's job; the only thing more shocking than Jesus's command that his disciples wash one another's feet is that he actually washed their feet. Later, John tells us that as Jesus walked with his disciples from Jerusalem and through the nearby Kidron valley, he told them, "greater love has no one than this: that he lays down his life for his friends." The idea is that followers of Jesus are commanded, in love, to voluntarily lay down status, rank, privilege, and even life itself, for one another, exactly the way Jesus did for us. That is the new commandment.
The grounds and the implications of this new commandment are particularly hammered out in John's account of the Maundy Thursday dinnertable dialectic between Jesus and Peter -- hotheaded, think-out-loud Peter. Peter was the one who at the foot-washing spoke the question everyone else must have been thinking: "Do you wash my feet?" Then he went one better and emphatically refused the foot-washing: "You shall never wash my feet. Not ever." Submitting to the menial service offered by his master was too much and he balked. But when Peter finally consents to have Jesus wash his feet, he plays one-up again and says, "not my feet only, also my hands and head!" One commentator* wrote that Peter's response here is like "improving" a u-turn by adding another 180 degrees. Peter, who is nothing if not a natural leader, cannot simply accept his master's service to him, perhaps because he starts to see that in so doing, he'll be swallowing a total inversion of all his ideas about power and leadership. He would have to take his first steps into a world -- in the gospels called "the Kingdom of God" -- where the new commandment was not just a nice lofty ideal, but, simply, the sensible way of life.
Peter's denials of Jesus are often chalked up to simple cowardice. The gospel accounts of Maundy Thursday don't let us get away with such a shallow analysis. Peter was utterly sincere when told Jesus, "I will lay down my life for you." But he didn't know what he was saying, and he got the roles exactly reversed. It would first be Jesus's part to lay down his life for Peter, the part of the greater to lay down his life for the lesser, the leader's part to lay down his life for his follower. Peter doesn't get this. And so he's sort of in the shoes of an attentive first-time viewer of an M. Night Shyamalan film, just before the film's climax: he knows the events well, up to this minute, but he still has no understanding of the story.
* Lesslie Newbigin