Taking communion when you shouldn't can get you killed:
1 Corinthians 11
23For I have received of the Lord that which also I delivered unto you, that the Lord Jesus the same night in which he was betrayed took bread:
24And when he had given thanks, he brake it, and said, Take, eat: this is my body, which is broken for you: this do in remembrance of me.
25After the same manner also he took the cup, when he had supped, saying, this cup is the new testament in my blood: this do ye, as oft as ye drink it, in remembrance of me.
26For as often as ye eat this bread, and drink this cup, ye do shew the Lord's death till he come.
27Wherefore whosoever shall eat this bread, and drink this cup of the Lord, unworthily, shall be guilty of the body and blood of the Lord.
28But let a man examine himself, and so let him eat of that bread, and drink of that cup.
29For he that eateth and drinketh unworthily, eateth and drinketh damnation to himself, not discerning the Lord's body.
30For this cause many are weak and sickly among you, and many sleep.
31For if we would judge ourselves, we should not be judged.