Obedience. Moses recounts the drama of the fire and darkness out of which God spoke and gave the ten commandments, which he quotes in full.
I was struck by the universal, profound nature of them. Not killing, stealing, taking your neighbours property. I mean the are very very ancient rules, we haven’t progressed beyond acknowledging them as true, and regularly breaking them, in 1000s of years. They are still an accurate mirror of our ideals and weakness.
He recounts how right the reaction of the people was. They were overwhelmed at hearing God’s voice, they were afraid to see him. They backed off and let Moses complete the interaction.
He calls them to have this respect again, to the law, to the words of God. He’s reminding them that the law came from the living God who is awesome and that is why it should be obeyed.