Source: Shaheed Murtada Mutahhari, The Narrative of Veracious, Vol.1, STORY, NO.60, p.137-138
'Isa ('a) said to his apostles: “I have a request to you, if you promise to do that, I will tell you."
The apostles said in reply: “We are obedient to you; we will obey your orders!”
'Isa ('a) stood up and began to wash the feet of each one of his apostles. The apostles felt deeply annoyed since they had promised to agree with him. They yielded to the circumstances. After 'Isa ('a) finished washing their feet, the apostles said: “You are our teacher. It was worthy of us to wash your feet, not you to wash ours!”
'Isa ('a) said: “I did it so that you would know the one deserves to undertake the people's services is the learned and the most dignified amongst you people. I did it to show you my humility and to teach you the lesson of modesty, for you would perform your duties in a humility manner and serve the people when you will be in charge of the people's instruction and guidance after me.
“Wisdom basically grows in the bosom of humility, not of haughtiness, just as the plants grow in the soft earth rather than the hard one.”(1)