Q . 54. What are we especially taught by these words, “before me,” in the first commandment?

A. These words, “before me”, in the first commandment, teach us, that God, who sees all things, takes notice of, and is much displeased with the sin of having any other God.

But if your heart turns away, and you will not hear, but are drawn away to worship other gods and serve them,  I declare to you today, that you shall surely perish. You shall not live long in the land that you are going over the Jordan to enter and possess.  Deuteronomy 30:17-18

If we had forgotten the name of our God
or spread out our hands to a foreign god,
would not God discover this?
For he knows the secrets of the heart.
Psalms 44:20-21

You have set our iniquities before you,
our secret sins in the light of your presence.
Psalms 90:8