“Thou shalt have not other gods before me.” Exodus 20:3
“The simple meaning of this commandment is, You shall worship me alone as your God. What do these words mean and how are they to be understood? What is it to have a god, or what is God?
Answer: A god is that to which we look for all good and where we resort for help in every time of need; to have a god is simply to trust and believe in one with our whole heart. As I have often said, the confidence and faith of the heart alone make both God and an idol. If your faith and confidence are right, then likewise your God is the true God. On the other hand, if your confidence is false, if it is wrong, then you have not the true God. For the two, faith and God, have inevitable connection. Now, I say, whatever your heart clings to and confides in, that is really your God.”
Martin Luther in Luther’s Large Catechism: God’s Call to Repentance, Faith and Prayer trans. John Nicholas Lenker (Minneapolis: Luther Press, 1908) 44.