Exodus 20:3 (NET) - You shall have no other Gods before Me.
In the ten commandments, God is very clear about how he feels when it comes to idolatry.
God both rightfully expects and demands to be first in our lives.
But what constitutes idolatry?
While Moses was up on Mount Sinai, the people convinced Aaron to make a calf out of gold so that they could worship it.
Exodus 32:4 (NET) - He accepted the gold from them, fashioned it with an engraving tool, and made a molten calf. Then they said, "These are your gods, O Israel, who brought you up out of Egypt."
It does not take a tremendous leap...