They tell their children about the faithfulness of God. You need to instruct your children. Fathers need to do that. To teach the truth Fathers must be Knowledgeable in the truth. You can't tell your children the truth of God if you don't know it in your heart.
Good fathers know the Bible.
You men have a Bible, read the Bible, study the Bible and become a man of the Book. Your Bible ought to be true, too. The best Fathers also know Jesus through His word. Let your family see you reading the Bible. Teach them the word.