For Lutherans the dichotomy of Law and Gospel is essential. And the Bible contains both: It contains instruction and commandments (e.g. "Love one another as I have loved you") and it contains promises (e.g. "God demonstrates His love for us in that while we were still sinners Christ died for us"). So, yes, the Bible does contain instructions, commandments; but the purpose of the Law is first and foremost to reveal to us our sin and our inability to abide in the obedience we are called to have toward God; God says "Do this" and we do not do it, we sin, we fall short, we err. Our salvation is found exclusively by the Gospel, what Christ has done for us apart from ourselves, it is grace alone on Christ's account alone.
Rightly dividing the word of truth, making the distinction between Law and Gospel is fundamental. Scripture contains both. And so there is Law which tells us what we must do, and thus reveals that we do not do it, driving us to despair and sorrow over our sin leading us to repentance; and there is Grace lifting us up in Christ by His glorious work to God clothing us with the righteousness of Jesus and thereby making us just. These two words, the word of God's law and the word of God's grace are found; both fundamentally lift up Christ. Christ who alone is the Just One who makes the unjust just by the grace of God through His all sufficient and glorious work and obedience; that by His death and resurrection we are justified and sanctified and made children of God in Him. It is always about Jesus.
-CryptoLutheran