A child was the least significant person in Jewish and in Greco-Roman culture. [1] By using a child as His object lesson, Jesus was saying that service involves caring about people, even insignificant people such as children. The same Aramaic word means both "child" and "servant." [2][source]
"Jesus was one of the first ever to see how essentially precious any person Isaiah , particularly a young child. A concern for children was not invented by the welfare state: it goes back to the teaching of Jesus." [3][source]
Jesus proceeded to compare the humblest of His disciples to the child (cf. Mark 9:42). This was the focus of Jesus" teaching that Matthew recorded (cf. Matthew 18:3-14). [source][source][source]