Deuteronomy is Moses’ farewell address to the Israelites. One idea he says over and over is the need to obey the LORD in the land that He will be giving you. God keeps his promises; it will be hard for the nation (and for us) to keep our promises and vows.
In Chapters 16-17, God describes the way you are to offer sacrifices, and the place you are to do it – the place that He will choose. Fear the Lord. Don’t fall prey to the worship practices of the people you are replacing, because God hates their fertility rites and Asherah poles and burning their children in the fire.
In Chapters 17-18, God lays out basics for the governance system for the nation. Take your hard cases to the priests and judges, who are the LORD’s representatives. Obey the decisions; if you don’t, then you deserve further punishment.
It will be acceptable to have a king, but only one whom God appoints. Be careful lest the king ignores the LORD; that will be bad for everyone. The king needs to read the book of the law all the days of his life – this will be the source of his wisdom. The king also needs to fear the LORD by following His laws.
Make sure the priests and Levites are taken care of. They get a portion of the sacrifices instead of an allotment of land; they are His chosen ones to teach and conduct worthy worship. Don’t move the land boundaries; always have two witnesses when judging a crime; establish safe havens for those who accidentally kill another. Make your judgments fit the crime – no more than a tooth for a tooth or an eye for an eye.
Some of the laws seem wacky and foreign to our twenty-first century “sensibilities.” But as Psalm 119 says over and over, these laws are a delight – they are a light unto our path. At least one lawyer came to saving faith because he could see the justice and benefits for the people in these laws. The fear of the LORD is the beginning of wisdom.