Mark 9:33-35

They arrived at Capernaum; and when He was in the house, He asked them, “What were you discussing and arguing about on the road?” [Matt 18:1-5; Luke 9:46-48] But they kept quiet, because on the road they had discussed and debated with one another which one [of them] was the greatest. Sitting down [to teach], He called the twelve [disciples] and said to them, “If anyone wants to be first, he must be last of all [in importance] and a servant of all.”