Mark 9:30-37 (NRSV):

30 They went on from there and passed through Galilee. He did not want anyone to know it; 31 for he was teaching his disciples, saying to them, “The Son of Man is to be betrayed into human hands, and they will kill him, and three days after being killed, he will rise again.” 32 But they did not understand what he was saying and were afraid to ask him.

33 Then they came to Capernaum; and when he was in the house he asked them, “What were you arguing about on the way?” 34 But they were silent, for on the way they had argued with one another who was the greatest. 35 He sat down, called the twelve, and said to them, “Whoever wants to be first must be last of all and servant of all.” 36 Then he took a little child and put it among them; and taking it in his arms, he said to them, 37 “Whoever welcomes one such child in my name welcomes me, and whoever welcomes me welcomes not me but the one who sent me.”