Yahweh revealed himself to Israel at Mount Sinai and audibly spoke the ten commandments.
His first words were that he is Yahweh their God and that they should have no other gods before him.
The first generation failed miserably to worship only Yahweh without idolatry as the golden calf incident showed.
To the second generation, Moses gave the Shema with instructions to teach it to their children diligently.
To this day Jewish people in Israel and throughout the world are devoted to the truth of the Shema.