1st Corinthians 11:23-31 is the text David uses today as we come together for the Lord's Supper.
23 For I pass on to you what I received from the Lord himself. On the night when he was betrayed, the Lord Jesus took some bread24 and gave thanks to God for it. Then he broke it in pieces and said, “This is my body, which is given for you. Do this to remember me.”25 In the same way, he took the cup of wine after supper, saying, “This cup is the new covenant between God and his people—an agreement confirmed with my blood. Do this to remember me as often as you drink it.”26 For every time you eat this bread and drink this cup, you are announcing the Lord’s death until he comes again.27 So anyone who eats this bread or drinks this cup of the Lord unworthily is guilty of sinning against the body and blood of the Lord.28 That is why you should examine yourself before eating the bread and drinking the cup.29 For if you eat the bread or drink the cup without honoring the body of Christ, you are eating and drinking God’s judgment upon yourself.30 That is why many of you are weak and sick and some have even died.31 But if we would examine ourselves, we would not be judged by God in this way.32 Yet when we are judged by the Lord, we are being disciplined so that we will not be condemned along with the world.