As we prepare to read Deuteronomy, the last book of the Pentateuch (Genesis-Deuteronomy), it is vital to hold on to the thread of covenant. Think of rock climbers who tether themselves together in order that their corporate ascent is safeguarded against dangerous falls. It is vital that we don’t minimize this theme of God’s covenant. The whole book of Deuteronomy is presented in the same treaty form which suzerain kings of the ancient near east would use; the main difference being that where ancient kings would form a treaty between themselves and their vassals/people calling the gods to be witness to the covenant and bring down judgement on those who would break the covenant, this covenant was between the people of Israel and God Himself. God was to be their king.
The reality is that from the fall in Eden onwards God dealt with man via gracious covenants. Noah, Abram, Jacob, Moses, and later David and Solomon all have this covenant between God and His people renewed. So what is this covenant? The Westminster Confession describes it as “the covenant of grace; wherein [God] freely offereth unto sinners life and salvation by Jesus Christ (WC Chapter 7.3).”
In essence, God always and only saves man through His Son the Christ. Further, man’s salvation is and always has been––even under these Old Testament iterations of the covenant of grace––a gracious gift and entirely unmerited. The covenant is recapitulated throughout Genesis, then further expanded in the giving of the Law on Sinai, and then we are brought to Deuteronomy where the covenant is renewed as Israel is about to enter the land which God had promised them. In Deuteronomy we have Moses preaching through the Ten Commandments, and reminding Israel that their salvation, deliverance and union with God is based entirely upon God’s free grace. Their obligation is––as the old Gospel song put it––to trust and obey.