1 Corinthians 2:14

2:14 The unbeliever does not receive the things of the Spirit of God, for they are foolishness to him. And he cannot understand them, because they are spiritually discerned.

1 Corinthians 10:20-21

10:20 No, I mean that what the pagans sacrifice is to demons and not to God. I do not want you to be partners with demons. 10:21 You cannot drink the cup of the Lord and the cup of demons. You cannot take part in the table of the Lord and the table of demons.

1 Corinthians 14:22

14:22 So then, tongues are a sign not for believers but for unbelievers. Prophecy, however, is not for unbelievers but for believers.