Theophylact of Ohrid — as excerpted in the Catena Aurea on Mark 9:30-37

“For His wish is not that we should usurp for ourselves chief places, but that we should attain to lofty heights by lowliness. He next admonishes them by the example of a child’s innocence; wherefore there follows: And he took a child, and set him in the midst of them.”