Not long after I was baptised, my Pastor at the time advised me to get stuck in to the book of Deuteronomy, on the grounds that this book is the key to the OT. Great advice. Since then I've spent a lot of time in this foundational charter of the life of Israel. This covenant document explains the history of Israel and underpins the prophetic critiques and warnings of Israel's national life. So what does Deuteronomy have to say about the Law?
1. The relationship between Yahweh and Israel is not fundamentally based on Law. The historical preamble to the covenant (chapters 1 to 3) makes it clear that if this were the case Israel would be doomed - it is a sorry history of rebellion, focussed on the idolatry committed at the very foot of Horeb. That Israel's entry into covenant with Yahweh is in fact based on a unilateral elective action of God is made clear in, for example, Deut 7:6-11 and Deut 9:4-12. This is good news for Israel, because it extends hope for restoration after the prophesied exile which will follow their neglect of the Law - Deut 30:1-10.
2. The Law which is given to Israel is good for them. In Deut 8:1-10, for example, a description of the blessing which Yahweh has showered on Israel in the wilderness, and which he will multiply to them in the land, is intermingled with the a description of the Law. The Law will be the foundation of Israel's reputation for greatness and wisdom amongst the nations - Deut 4:6-8. Moreover, the keeping of the Law is repeatedly associated with rejoicing, for example the giving of the tithe.
3. Israel can keep the Law. When Moses says 'What does Yahweh require of you..?' and proceeds to list a series of things including keeping all the statutes and commandments of the Law (Deut 10:12-13), it is clear from the context that we are meant to think that this is only the minimum which ought to follow from the goodness of God which has been recounted in previous chapters. By the time we get to chapter 30, Moses is able to say "this commandment is not too hard for you". Nothing too difficult has been asked of Israel. They can keep this Law, and moreover it makes no sense for them not to do so - it flows logically from the grace they have been shown in the past, and carries with it promises of future blessing.
4. Israel will not keep the Law. Moses' last recorded words are a blessing on the tribes of Israel; but before this he has seen into their future, and given them a song which predicts their future apostasy. Indeed, Moses knows that after his death Israel "will do what is evil in the sight of Yahweh" (Deut 31:24-29). Why? Not because the Law is too hard for them, but because their hearts are not right - they have not yet been given a heart to obey (Deut 29:4). This is a promise for the future (Deut 30:6), after the exile. A time is envisaged when Israel will be changed and will keep the Law.
As well as helping us to understand the OT, isn't this important for our understanding of the NT?