Jesus is demonstrating, as he washes the feet of his disciples, that the greatest among them (definitely him!) should be willing to serve all the rest. None of them are higher than Jesus, and none of them have ever stooped lower than he is in that moment. So much so, it alarms Peter. As Jesus tells them that they should love one another, that is the completion of the thought: putting the other first, never shoving ahead to get your own way. It Jesus can do that, we should be able to as well.