The Ten Commandments are a summary of the entire old covenant law (Eugene Merrill). It is as if, in these ten commands, God gave bullet points to His people that encapsulated the heart of His covenant with them. They were God’s instructions for the lives of His old covenant people and continue in their relevance for us today.
In our use of the Ten Commandments, we will be following the format of the reformer Martin Luther. Luther would use the Ten Commandments for instruction, asking how this particular command might teach him and apply to his life. He would then give thanks based on the instruction that he had pulled from the command.
Next he would confess the sins that the command might bring to light. And finally he would turn these concepts to prayer. We will do the same. (This devotional has been generally influenced by Martin Luther, John Calvin, John Frame, and Ron Mehl.)
As we look at the Ten Commandments, there are a couple of things that we must remember. First, we must always remember that we are in a different place in redemptive history. As the charter of the old covenant, the law has passed away with the coming of the new covenant (1 Cor 9:20; Gal 3:23-26). But the law is also inspired Scripture, and Scripture never loses its relevance—even if the situation in which it was initially given no longer applies (Schreiner, Gentry/Wellum, Rosner, Garrett). As Scripture, God still uses His law in our lives even now.
Second, we are not made right with God by obeying the law, but through faith in Jesus (Rom 3:28)! The law was designed by God to point us to Jesus. So as we move through the Ten Commandments and look at practical applications of them, we must never forget the most important point that God is teaching us through them. In the overall flow of Scripture, we are being taught by these commandments that we are sinners and need a Savior. They teach us that we cannot live up to God's standards and so we need to turn in faith to Jesus and the cross.