1 Corinthians 10 v 19-21


1 Corinthians 10:19-21 
(19)  What say I then? that the idol is any thing, or that which is offered in sacrifice to idols is any thing? 
(20)  But I say, that the things which the Gentiles sacrifice, they sacrifice to devils, and not to God: and I would not that ye should have fellowship with devils. 
(21)  Ye cannot drink the cup of the Lord, and the cup of devils: ye cannot be partakers of the Lord's table, and of the table of devils. 


10:19-21. The same was true of pagan worship. It was true that an idol was nothing (8:4; cf. Ps. 115:4-7), but the ultimate reality behind pagan religion was demonic. Pagan sacrifices were offered to demons, not to God. Through his minions “the god of this age” blinded unbelievers and kept them from the truth (2 Cor. 4:4). There could be no union for good between Christ and Belial (2 Cor. 6:15). So those who were the temple of God (1 Cor. 3:16; 6:19) should shun the temple of idols (cf. 2 Cor. 6:14-18). No magical contamination was conveyed, but the corrupt character of the participants would be harmful for believers (1 Cor. 15:33). Being participants with demons was unthinkable for those who are participants with Christ (10:21; cf. v. 16). 

Excerpt from: 
Walvoord, J. F., Zuck, R. B., & Dallas Theological Seminary. (1983-c1985). 
The Bible Knowledge Commentary : An Exposition of the Scriptures. 
Wheaton, IL: Victor Books.