With the original generation of adult Israelites now dead, Moses called the people together to renew the covenant made with God at Mount Sinai (see Deut 29:12) with its blessings and its curses.
In a glimpse of Jesus’ high standards, Moses made it clear that God would not tolerate lipservice. It wouldn’t be enough to obey the letter of the law but ignore its spirit:
29:19-20 Those who hear the warnings of this curse should not congratulate themselves, thinking, ‘I am safe, even though I am following the desires of my own stubborn heart.’ This would lead to utter ruin! The Lord will never pardon such people. Instead his anger and jealousy will burn against them. All the curses written in this book will come down on them, and the Lord will erase their names from under heaven.
It goes back to the first of the ten commandments: it would be impossible to worship God by just complying with the letter of the law. It had to come from the heart. Moses made this clear later in his sermon:
30:20 You can make this choice by loving the Lord your God, obeying him, and committing yourself firmly to him. This is the key to your life.
And there was no excuse for not knowing. It was all laid out, on stone tablets and scrolls; and there were daily, weekly, monthly and annual reminders in the form of sacrifices, offerings, festivals and feasts:
30:11-14 This command I am giving you today is not too difficult for you to understand, and it is not beyond your reach. It is not kept in heaven, so distant that you must ask, ‘Who will go up to heaven and bring it down so we can hear it and obey?’ It is not kept beyond the sea, so far away that you must ask, ‘Who will cross the sea to bring it to us so we can hear it and obey?’ No, the message is very close at hand; it is on your lips and in your heart so that you can obey it.