A.T. Robertson Commentary Matthew 18:4

"Whosoever therefore shall humble himself as this little child, the same is the greatest in the kingdom of heaven." — Matthew 18:4 (ASV)

This little child (το παιδιον τουτο). This saying about humbling oneself Jesus repeated a number of times as for instance in Mt 23:12. Probably Jesus pointed to the child by his side. The ninth-century story that the child was Ignatius is worthless. It is not that the child humbled himself, but that the child is humble from the nature of the case in relation to older persons. That is true, however "bumptious" the child himself may be. Bruce observes that to humble oneself is "the most difficult thing in the world for saint as for sinner."