1. The selfishness of their observance
17 But in the following instructions I do not commend you, because when you come together it is not for the better but for the worse. 18 For, in the first place, when you come together as a church, I hear that there are divisions among you. And I believe it in part, 19 for there must be factions among you in order that those who are genuine among you may be recognized. 20 When you come together, it is not the Lord’s supper that you eat. 21 For in eating, each one goes ahead with his own meal. One goes hungry, another gets drunk. 22 What! Do you not have houses to eat and drink in? Or do you despise the church of God and humiliate those who have nothing? What shall I say to you? Shall I commend you in this? No, I will not. 1 Corinthians 11:17–22 (ESV)

2. The symbolism of the ordinance
23 For I received from the Lord what I also delivered to you, that the Lord Jesus on the night when he was betrayed took bread, 24 and when he had given thanks, he broke it, and said, “This is my body, which is for you. Do this in remembrance of me.” 25 In the same way also he took the cup, after supper, saying, “This cup is the new covenant in my blood. Do this, as often as you drink it, in remembrance of me.” 26 For as often as you eat this bread and drink the cup, you proclaim the Lord’s death until he comes. 1 Corinthians 11:23–26 (ESV)

3. The seriousness of their offence
27 Whoever, therefore, eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty concerning the body and blood of the Lord. 28 Let a person examine himself, then, and so eat of the bread and drink of the cup. 29 For anyone who eats and drinks without discerning the body eats and drinks judgment on himself. 30 That is why many of you are weak and ill, and some have died. 31 But if we judged ourselves truly, we would not be judged. 32 But when we are judged by the Lord, we are disciplined so that we may not be condemned along with the world. 33 So then, my brothers, when you come together to eat, wait for one another— 34 if anyone is hungry, let him eat at home—so that when you come together it will not be for judgment. About the other things I will give directions when I come. 1 Corinthians 11:27–34 (ESV)

First, Christians should examine themselves, not to find reasons they are unworthy, but to find evidence of a repentant heart—evidence that grace is at work. (S.T. Um)

Second, partaking of the Lord’s Supper is to discern the Lord’s body in the process (11:29). It means we recognize that the elements symbolize the body and blood of Christ and salvation comes only from his death on the cross (Roger Ellsworth

23 Search me, O God, and know my heart! Try me and know my thoughts! 24 And see if there be any grievous way in me, and lead me in the way everlasting! Psalm 139:23-24 (ESV)

Third, a person must “judge the body rightly” (1 Cor. 11:29) . . . the context suggests that Paul is referring to treating the corporate “body of Christ,” the church, in a respectful and dignified manner.

 Fourth, the observers must “wait for one another” (11:33). Each member of the church must look out for the interests of others.

 Fifth, in closing, Paul accompanies his strong warning with a comforting promise. Instead of becoming weak and sick or dying, they will experience the blessing of the cup as they fellowship with God and one another around this sacred Table (10:16). (Chuck Swindoll)