1 Corinthians 10:16, 21

Is the cup of blessing which we bless [at the Lord’s Supper] not a sharing in the blood of Christ? [Indeed it is.] Is the bread which we break not a sharing in the body of Christ? [Indeed it is.]

You cannot drink [both] the Lord’s cup and the cup of demons. You cannot share in both the Lord’s table and the table of demons [thereby becoming partners with them].