1 Corinthians 10 : 18 Behold Israel after the flesh: are not they which eat of the sacrifices partakers of the altar? 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.

Paul is again telling these people that they ate from the temple when they used to sacrifice but now it is not  necessary and if they eat of that sacrifice now they worshiping an idol. He goes on to say that an idol can be anything and to worship that idol means you are worshiping nothing because an idol is nothing. When Paul mentions the gentiles here he is talking about the heathen world and they sacrifice or worship they are worshiping devils. They do this because they know not God. Christians should not have anything to do with demons or devils in any way because they belong to God. We really need to aware of the things and people we  keep company with that we do not give the devil a chance to lure us away from God.