Psalm 78:1-8

My people, hear my teaching;
    listen to the words of my mouth.
2 I will open my mouth with a parable;
    I will utter hidden things, things from of old—
3 things we have heard and known,
    things our ancestors have told us.
4 We will not hide them from their descendants;
    we will tell the next generation
the praiseworthy deeds of the Lord,
    his power, and the wonders he has done.
5 He decreed statutes for Jacob
    and established the law in Israel,
which he commanded our ancestors
    to teach their children,
6 so the next generation would know them,
    even the children yet to be born,
    and they in turn would tell their children.
7 Then they would put their trust in God
    and would not forget his deeds
    but would keep his commands.
8 They would not be like their ancestors—
    a stubborn and rebellious generation,
whose hearts were not loyal to God,
    whose spirits were not faithful to him.
 

This psalm recounts the history of Israel from its deliverance from Egypt to the kingship of David. Its negative lesson is that this history not be repeated in the lives of the listeners. The positive lesson is that believers be marked by true faith. We should not just know the truth about who God is but must trust him from the heart and show this  saving faith through a changed life of obedience. Throughout history many have honored God with external behavior but failed to have converted hearts (Isaiah 29:13; Jeremiah 4:4). Are you just going through the motions of religion, or have you been born again (John 3:1-16)?