The holy Rimanover taught: Children of excellent religious upbringing often times become impious. Why is this so? Is it not taught that if a child receives a good upbringing it will become habitual with him and he will not forsake it in maturity (Proverbs 22:6)?
The reason for the impiety of children is that often they are raised on money dishonestly gained. When they grow up, they imitate their parents and live with out any sense of honesty (Emet l'Yaakov, page 48).
The Three Weeks lead us into the Hebrew month of Av, which means, parent. Our tradition teaches us that one of the consequences of exile is the breaking of the connection between parent and child. It is therefore important to use this period of the Jewish calendar to focus on our role as Av, parents. The Rimanover is reminding us how significant honesty is in maintaining and nurturing the natural connection between parent and child so that the child will the values practice important to his parents.