1 Corinthians 11:27-31

Wherefore whosoever shall eat the bread or drink the cup of the Lord in an unworthy manner, shall be guilty of the body and the blood of the Lord. But let a man prove himself, and so let him eat of the bread, and drink of the cup. For he that eateth and drinketh, eateth and drinketh judgment unto himself, if he discern not the body. For this cause many among you are weak and sickly, and not a few sleep. But if we discerned ourselves, we should not be judged.