1 Corinthians 8:4

So, as to eating things that have been sacrificed to idols, we are sure that an idol is nothing in the world, and that there is no God but One.

1 Corinthians 10:19-20

Then what do I mean? That the sacrifice to an idol is a reality, or that an idol itself is a reality? Of course not!

1 Timothy 4:1

Now the Spirit distinctly declares that in later times some will turn away from the faith, because they continuously give their attention to deceiving spirits and the things that demons teach

Revelation 9:20

But the rest of mankind, who were not killed by these plagues, did not repent of the works their hands had done, so as to give up worshiping demons and idols of gold, silver, bronze, stone, and wood, which cannot either see or hear or move;

Treasury of Scripture Knowledge

Summary

They sacrificed unto devils, not to God; to gods whom they knew not, to new gods that came newly up, whom your fathers feared not.

Bible References

Sacrificed

1 Corinthians 10:20
I mean that what the heathen sacrifice they sacrifice to demons, not to God, and I do not want you to be in fellowship with demons.
1 Timothy 4:1
Now the Spirit distinctly declares that in later times some will turn away from the faith, because they continuously give their attention to deceiving spirits and the things that demons teach
Revelation 9:20
But the rest of mankind, who were not killed by these plagues, did not repent of the works their hands had done, so as to give up worshiping demons and idols of gold, silver, bronze, stone, and wood, which cannot either see or hear or move;

Not to god

1 Corinthians 8:4
So, as to eating things that have been sacrificed to idols, we are sure that an idol is nothing in the world, and that there is no God but One.
1 Corinthians 10:19
Then what do I mean? That the sacrifice to an idol is a reality, or that an idol itself is a reality? Of course not!