What this means: You shall have Me alone as your God. What is the meaning of this, and how is it to be understood? What does it mean to have a god? Or, what is God? Answer: A god means that from which we are to expect all good and in which we are to take refuge in all distress. So, to have a God is nothing other than trusting and believing Him with the heart. Confidence and faith of the heart alone make both God and an idol. If your faith and trust is right, then your god is also true. On the other hand, if your trust is false and wrong, then you do not have the true God. For these two belong together, faith and God ["Whoever would draw near to God must believe that he exists and that he rewards those who seek him." Hebrews 11:6]. Whatever you set your heart on and put your trust in is truly your god.
The purpose of this commandment is to require true faith and trust of the heart, which settles upon the only true God and clings to Him alone. It is like saying, "See to it that you let Me alone be your God, and never seek another." In other words, "Whatever you lack of good things, expect it from Me. Look to Me for it. And whenever you suffer misfortune and distress, crawl and cling to Me. I, yes, I, will give you enough and help you out of every need. Only do not let your heart cleave to or rest on any other." (paragraphs 1-4)
Condensed from CONCORDIA: THE LUTHERAN CONFESSIONS, copyright 2005,2006 by Concordia Publishing House. Used by permission. All rights reserved. To purchase a copy of CONCORDIA, call 800-325-3040.