Motivation and enablement for obedience to the Lord in the Old Testament are no different from that in the New Testament, and it is proven in the preface to the Ten Commandments.
I. The Lord
The most obvious reason to obey God’s commandments is that it is God who gave them.
Knowing: “I am the Lord,” he says, using that sacred, stunning name YHWH by which he first revealed himself to Moses at the burning bush. “I am that I am” is derived from that name. In saying this, he was declaring his absolute uniqueness, absolute sovereignty, and aseity—his total self-sufficiency.
Being: As our Creator each of us is born with a covenant obligation to obey the Lord. We owe him obedience as an act of gratitude for bringing us into existence.
Doing: John Calvin called the guiding work of the law its “third use.” While he compared its “second use” to a whip that drives us to Christ for conversion, he compared the law’s third use to a lamp, which guides our feet along the safest path. Which of these metaphors for the law generally describes how you think about the law?
II. Your God
When the Holy Spirit weds us to Jesus we are restored to the loving covenantal relationship God always intended for his image bearers.
Knowing: God described his intention for the law from the very beginning in positive terms. He called them “words of life” (Dt. 32:47). When Moses brought the laws to God’s people, he urged them to obey them "so that you may live and prosper and prolong your days in the land that you will possess" (Dt. 5:32-33; Dt. 30:19).
Being: Instead of the laws being our enemy any longer, they become our Father’s household rules for healthy, happy, and fulfilling living.
Doing: God’s law not only mitigates the harm we can bring on ourselves, it prescribes a way of life that tends toward flourishing. Which of these purposes of the law define the way you generally view it?
III. The Redeemer
The third and most obvious reason to obey the Ten Commandments is Christ is our Redeemer.
Knowing: Before God gives his people these commandments, he reminds them how much he loves them. In effect he says, “If you doubt I want what is best for you, remember I brought you out of Egypt. And remember I did so with the blood of an innocent victim foreshadowing the blood of my Son, my precious lamb, I would someday sacrifice finally for all my people.”
Being: Each commandment finds an even fuller expression of God’s love personified in Jesus.
Doing: How do you see God’s love personified in Jesus in each of the Ten Commandments? What scriptures show you this?