"I came into the world not to call the righteous but sinners to repentance." The voice of Jesus then repeated words that need no interpreter. They were the words Christ spoke to the Scribes and the Pharisees who complained to His disciples when they saw Him (their Master-Matthew 9:12) eating with Publicans and Sinners: "They that are whole need not a physician; but they that are sick." (Luke 5:31)
The voice of our Lord then compared little children to one who needs no physician; "Little children are whole, for they are not capable of committing sin." Baptism is for the remission of sins, therefore, to baptize little children for the remission of sins which they did not commit, and could not, is to hold God to ridicule, and make a "solemn mockery" of His goodness and mercy.