D.L. Moody emphasizes the powerful influence of parental behavior on children, illustrating this with a story about a child imitating their mother breaking a tumbler. He warns that children learn not only through direct teaching but also by observing their parents' actions, which can lead to negative behaviors such as breaking the Sabbath or lying. Moody calls for parents to model the values they wish to instill in their children, as imitation plays a significant role in their moral development.