What does Deuteronomy 4:40 mean?

Keep his rules and commands that I’m giving you today, so things will go well for you and your children after you, and you’ll live a long time in the land the Lord your God is giving you forever. Deuteronomy 4:40 - Modern Text Bible

(Obeying God’s commands isn’t just about rules—it’s about their future, their kids, and their security in the land.)