The most important lesson in life that parents can impress on their children is to love God with all their heart, mind and soul and their neighbour as themselves.
“Teacher, which commandment in the law is the greatest?”
Jesus said to him, “You shall love the Lord, your God, with all your heart, with all your soul, and with all your mind. This is the greatest and the first commandment.
The second is like it: You shall love your neighbor as yourself.
The whole law and the prophets depend on these two commandments.”
~ Matthew 22:36-40