Some have built an entire theology on the false assumption that when God commands us to obey or believe, we have the ability to obey or believe. So then, what's the point of all God's commands? They show us what the power of sin has done to us, how it controls us, and how it controls our every decision and action. We are "under the power of sin" as the Apostle Paul writes (Romans 3:9). This is our condition. We are sold under sin. Sin rules us. We serve sin. We have no choice. Sin is going to kill us and there's nothing we can do to stop it. This is why Paul cries out, "I am a wretched man! Who will deliver me from the body of this death?" (Romans 7:24)
God commands the impossible to stop us dead in our tracks. When he speaks a command, it shows us our inability to obey or believe as he commands us to obey and believe—with perfect obedience and trust from our heart. When God commands us, for example, to repent and believe the Gospel, he doesn't want us to respond with, "Okay, I'll get right on that. And, don't worry, I'm gonna do my best, you'll see." What he wants is for us to say, "But… that's impossible." Only then, when God reveals to us that we have nothing to offer him, nothing we can do to meet his expectations of perfect obedience and faith, that there's nothing lovable about us that would make him want to love us—only then when we've had the veil pulled back on our sin, are we ready to receive Christ. If we imagine we can obey God's command, or trust him in perfect faith, then Christ's perfect obedience and faith, which fulfilled all God's demands, was for nothing.
For Martin Luther, this Scriptural understanding of God's commands was vital for Christian faith. We are under the power of sin. Sold into slavery to sin, we've lost our ability to choose between God and the devil, faith and unbelief, grace and sin, promise and law, blessing and curse. We are compelled by the power of sin to always disobey and disbelieve God. And worse, when we assume we're free to choose between good and bad, right and wrong, in obedience to God's commands—we're actually standing in the place of God, knowing good and evil. We're not being obedient to God's commands, we're re-enacting the original sin. The Spirit alone works both blessings in us, regenerating us, and preserving us.
That doesn't mean what God commands is bad. No, "the commandments are not given inappropriately or pointlessly; but in order that through them the proud, blind man may learn the plague of his impotence, should he try to do as he is commanded" (Luther, The Bondage of the Will, in Packer & Johnston, pg. 160).
Only when God exposes our sin as being wholly sinful and we are tempted to give up hope of ever being saved from our doom, can we receive his saving grace that comes to us in the person of Jesus Christ. When God speaks his commands they are not given "inappropriately or pointlessly," Luther writes, "but in order that through them the proud, blind man may learn the plague of his impotence, should he try to do as he is commanded." (Packer, pg. 160)
The Spirit alone works both blessings in us, regenerating us, and preserving us. That's why Luther is of such help and encouragement for all of us who've ever been crushed by the responsibility we assume for living up to what God commands. He points out that, "man, before he is renewed into the new creation of the Spirit's kingdom, does and strives for nothing to prepare himself for that new creation and kingdom, and when he is re-created he does and strives for nothing towards his perseverance in that kingdom; but the Spirit alone works both blessings in us, regenerating us, and preserving us when regenerate, without ourselves..." (Packer, p. 268)
Search your Bible cover to cover and highlight every "if," underline every command, make a note of every "ought" and "should," and you will discover that God's word tells you what you are to do and not do. He tells you what is required of you. But nowhere does he say you have the power or ability to do anything about it. When God says, "If you are willing," he doesn't say you can or are willing. When God says, "If you are willing," "if you hear," "if you do," he doesn't then declare that you have the ability to do it, just that you're obligated to do it. But we can't, and that's what finally kills us.
The command is good because God speaks it, and God is good. But as Paul writes, "sin, having been afforded an opportunity through the commandment, deceived me and through it killed me" (Romans 7:11) It's not the command, but sin that deceives us, inspiring us to imagine we can do and not do what God commands. Sin stirs us up to believe we can be good and holy, because the command is good and holy, just as God is good and holy—and we can be like God, if we can only be more obedient and more faithful. Sin sells us on the lie that we have the ability, the freedom, to choose to obey God's commands.
When this happens, we even imagine that grace is given to us for the purpose of obedience. That God's grace is a spiritual steroid injected into us by the Spirit, to strengthen us for the Christian life, so we can perfectly obey and believe. All this serves to drive us away from God's grace. It drives us away from Christ, and deeper into sin, deeper into "the body of this death." And this is why we desperately need a Savior, one who will rescue us from our delusions of lawfulness. In fact, only through faith in Christ, without any effort or seeking on our part, do we fulfill all God's demands and commands to obey and believe perfectly (Romans 3:31).
God demands we be do-ers of his commands, not try-ers. He doesn't wink at sin either. His commands put us in an impossible position then, which is exactly where he wants us. He wants to expose the power of sin in our lives and our lawless ungodliness. Why? Because God loves to justify the ungodly! (Romans 4:5) It's not what God commands, but what Christ has done to fulfill God's commands in our place that finally matters. We are not expected to be doers of God's command, but believers in God's promise. The command turns us away from ourselves, and all our self-salvation projects, to hear what He promises us in Christ: forgiveness for our lawlessness, life rising up out of sin induced death, and salvation for those who've been shown they never had a chance at saving themselves by obeying God's commands.