Deuteronomy is largely a sermon, or set of sermons, preached by Moses to all of Israel shortly before his death and not long before the conquest of the land under the leadership of Joshua. It is a motivational sermon, urging Israel’s faithful obedience to the covenant laws of Sinai given 40 years previously.
The circumstance of the sermon carries added significance because of Israel’s failure, a generation earlier, to conquer the land starting at Kadesh-barnea on the southern border of Canaan (see Deut. 1:19–46). Now that they are back at the eastern border of the Promised Land, Deuteronomy seeks to ensure that such failure does not recur. The rhetorical style of the sermon motivates obedience by constantly reassuring them of God’s faithfulness and his power to keep his promise of land. This faithfulness of God remains despite Israel’s persistent sin, detailed at length (e.g., Deut. 1:19–46; 9:1–29). Thus Deuteronomy demonstrates that God’s faithfulness results in mercy to his sinful people, for the sake of his promises to Abraham.
The theology of Deuteronomy is focused on convincing Israel to trust and obey, and to conquer the land. The uniqueness and incomparability of God is clearly argued (e.g., ch. 4). His power over other nations and armies is evident (e.g., Deut. 2:1–23). His grace and faithfulness are also stressed, with frequent reminders that the land is sworn by him on oath and is undeserved (Deut. 9:4–6) and full of good things (e.g., Deut. 6:10–12).
The book’s emphasis on the continuation of the covenant made at Sinai with the previous generation underscores the abiding significance of God’s law for his people (e.g., see Deut. 5:1–3). The large central section of Deuteronomy (Deut. 12:1–26:19) recites the law, consistently urging Israel to keep it. The law is wide-ranging, incorporating all areas of life—economics, family and sexual relationships, religious observance, leadership, justice, guidance, food, property, and warfare. To some extent, the detail of the laws fleshes out the great command of Deuteronomy 6:5, that Israel is to love the Lord with all its heart, soul, and strength. Chapters 12–16 show what such total love of God will look like and, in many respects, provide examples of what the Ten Commandments (ch. 5) mean in practice.