Mark 10:35-45:

"Then James and John, the sons of Zebedee, came over and spoke to him.  "Teacher," they said, "we want you to do us a favor."
"What is your request?" he asked.
They replied, "When you sit on your glorious throne, we want to sit in places of honor next to you, one on your right hand and the other on your left."
But Jesus said to them, "You don't know what you are asking? Are you able to drink from the bitter cup of suffering  I am about to drink? Are you able to be baptized with the baptism of suffering I must be baptized with?"
"Oh yes," they replied, "we are able!"
Then Jesus told them, "You will indeed drink from my bitter cup and be baptized with my baptism of suffering.  But I have no right to say who will sit on my right or my left.  God has prepared those places for the ones he has chosen."
So Jesus called them together and said, "You know that the rulers in this world lord it over their people, and officials flaunt their authority over those under them.  But among you it will be different.  Whoever wants to be a leader among you must be your servant, and whoever wants to be first among you must be the slave of everyone else.  For even the Son of Man came not to be served but to serve others and to give his life as a ransom for many."