17 And he took the cup, and gave thanks, and said, Take this, and divide it among yourselves:
18 For I say unto you, I will not drink of the fruit of the vine, until the kingdom of God shall come.
19 And he took bread, and gave thanks, and brake it, and gave unto them, saying, This is my body which is given for you: this do in remembrance of me.
Luke 22:17-19 KJV
Do This in Remembrance
Right before Jesus was about to be arrested, He had supper with His disciples. He was teaching them about the New Covenant that He was making. This covenant would require Him to shed His blood for the forgiveness of sins. The bread is symbolic for His body that was broken for us. The cup, which He blessed, is symbolic for His blood.
Jesus gave a command that we do this in remembrance of Him. Remembering how He suffered for us and His body was broken. Also, His blood was shed for us. This is considered sacred to Christians and only those who believe and have been baptized in the name of the Lord should partake in communion. If someone is not a Christian and comes into the church, they should not partake in communion. We need to guard or protect what is Holy. (Matthew 7:6)
Some people say that we should only take communion at night time and that we must use wine when taking communion. If we do not do it this way then we are defiling communion.
I have a question. What about the Christians in prison who may only get one meal a day during the morning? If they decide to use their only meal as communion in remembering the Lord, are they in sin?
No, they are not in sin. Statements like that are petty. The command Jesus gave us was to do this in remembrance of Him. So, we eat the bread and drink from the cup remembering what our Lord and Savior has done for us.
It is important that we do self examine ourselves and confess any sins to Lord before we take communion. Let's see what Paul says about this.
27 So then whoever eats the bread or drinks the cup of the Lord in a way that is unworthy [of Him] will be guilty of [profaning and sinning against] the body and blood of the Lord.
28 Let a man [thoroughly] examine himself, and [only when he has done] so should he eat of the bread and drink of the cup.
29 For anyone who eats and drinks without discriminating and recognizing with due appreciation that [it is Christ’s] body, eats and drinks a sentence (a verdict of judgment) upon himself.
30 That [careless and unworthy participation] is the reason many of you are weak and sickly, and quite enough of you have fallen into the sleep of death.
31 For if we searchingly examined ourselves [detecting our shortcomings and recognizing our own condition], we should not be judged and penalty decreed [by the divine judgment].
1 Corinthians 11:27-31 AMPC