For in six days the LORD made heaven and earth, the sea, and all that in them is, and rested the seventh day: wherefore the LORD blessed the sabbath day, and hallowed it.
Exodus 20:11
"Isaiah describes idolatry as “folly” because there is only one God and beside him there is no other god, so it is foolish to trust in other deities (Isaiah 43:11, 44:6, 45:5).
More to the point, there are no other gods because the attribute that separates God from all other deities is that of creating (Isaiah 40:28, 42:5)."
AIG