You can't both drink the cup of the Lord and the cup of demons. You can't both partake of the table of the Lord, and of the table of demons.

In the same way he also took the cup, after supper, saying, "This cup is the new covenant in my blood. Do this, as often as you drink, in memory of me."

The cup of blessing which we bless, isn't it a sharing of the blood of Christ? The bread which we break, isn't it a sharing of the body of Christ?

For as often as you eat this bread and drink this cup, you proclaim the Lord's death until he comes.

Therefore whoever eats this bread or drinks the Lord's cup in a way unworthy of the Lord will be guilty of the body and the blood of the Lord.

But let a man examine himself, and so let him eat of the bread, and drink of the cup.