This is the fourth post on sacraments in my ongoing series, theology in bullet points. The first unit in this series had to do with God and Creation (book here), and the second unit was on Christology and Atonement.
We are now in the third and final unit: The Holy Spirit and the Church. The first set of posts in this final unit was on the Holy Spirit. The second set was on the Church. This third set is on sacraments.
Communion is a sacrament of re-empowerment.
1. Along with baptism, communion is the other practice that many Protestant churches consider to be a sacrament. It is the practice that remembers the Last Supper Jesus ate with his disciples before dying. Bread and wine (or juice) are consumed after the biblical words of that meal are spoken. It is often a time of reflection, even repentance, and the believer is renewed and strengthened to continue to walk with Christ and live a godly life through the power of the Holy Spirit.
The medium of communion is thus bread and wine.  The sacramental power of the Spirit is the power of renewal. The partaker is ideally renewed in faith and re-empowered by the Spirit.
2. On the one hand, communion is also a remembrance. The very first meal at the Last Supper of Jesus before his death was around the time of Passover.  It remembered the exodus and how God brought Israel out of slavery in Egypt.
For Christians, in this meal we especially "give thanks" for the fact that Jesus died for the sins of the world. Communion is often called the "Eucharist" or the "thanksgiving" for Jesus' death and the power it has made available for the believer. This is a power not only for salvation but also the power to defeat Sin.
Communion thus, in part, looks back. "Do this in remembrance of me," Jesus said on the night he was betrayed (e.g., 1 Cor. 11:24-25; Luke 22:19). In communion we remember Jesus' death on the cross.
The wine was the "new covenant" in Jesus' blood (1 Cor. 11:25; Luke 22:20). It remembers that his blood was "poured out for many" (Mark 14:24) and "for the forgiveness of sins" (Matt. 26:28). So also taking communion can be a time when any sins are forgiven again. It is a sacred moment ripe for any needed repentance and forgiveness.
Communion also looks forward to the "wedding banquet" that we will eat with Jesus when he returns and the kingdom of God fully comes to the earth as it is in heaven. Mark remembers Jesus telling his followers that night, "I will never again drink of the fruit of the vine until that day when I drink it new in the kingdom of God" (Mark 14:25). When we eat the bread and drink the cup, we thus look forward to the day when we will be with Christ in the kingdom of God on earth.
3. Like the Passover meal and the Last Supper meal, communion was probably a meal originally. 1 Corinthians 11 tells us of problems the Corinthian church had when they ate the Lord's Supper (1 Cor. 11:20). Enough wine was consumed by some that they became drunk, while others ended up hungry (11:21). This suggests that the meal was a full meal.
Jude 12 similarly mentions an agape or love-feast that was apparently customary for Christians. Likely this is another reference to the Lord's Supper as a meal. However, the solemnity of the event increased quickly, perhaps in part from the circulation of Paul's letter to the Corinthians. By the time of the Didache in the early second century, only those who are baptized are allowed to participate in this meal (9.5).  Eventually it would become a smaller ritual embedded within a worship service.
4. The word communion suggests one significance of the event, namely, the unity of the Church. This was the problem at Corinth. The wealthy and those with status in the community were eating their full and getting drunk, while slaves and those with little status presumably were those who went hungry (1 Cor. 11:21).  Paul even suggests that some have become sick and died in the community because of such contempt toward others (1 Cor. 11:30).
The unity of the body of Christ is thus a major connotation of "communion." Paul says words that are sometimes spoken during communion: "Because there is one bread, we who are many are one body, for we all partake of the one bread" (1 Cor. 10:17). This meaning of communion is sometimes obscured in the American church when individual wafers and cups are used for communion. The older, historic practice is for there to be one cup and one loaf of bread to signify the unity of the body of Christ. So also at the Last Supper, they passed the same cup and loaf around (e.g., Luke 22:19)
5. Paul urged the Corinthian church to examine themselves before they ate the bread and drank the cup of thanksgiving (1 Cor. 11:28). Some have found this admonition terrifying, especially since it is accompanied by a statement that some have died for eating unworthily. In some places, individuals will actually skip a church service if they know that communion will be served.
But Paul is not saying that one must have repented of all sin before taking communion. He was targeting the divisive way in which those at Corinth with high status were scorning those of low status in the communion meal. In truth, the act of communion is itself a highly appropriate moment during which one can repent of any sin and receive forgiveness. It is ripe for this renewal and re-empowerment for service and victory over temptation.
It seems likely that the earliest Christians came together to eat this agape at least once a week. We have good reason to believe that many Christians gathered early on Sunday morning, the "Lord's Day," to celebrate the resurrection. Pliny the Younger in the early second century mentions that Christians in northern Turkey met before dawn on a certain day, presumably Sunday, and then gathered together later to partake of a meal. (Letters 10.97). It thus seems likely that Christians ate the Lord's Supper every Sunday.
6. It is good for believers to eat together. Eating is a common human practice. In the first century, you ate together with those with whom you considered yourself one, whether family or the groups to which you belonged. This is why table fellowship was such a controversial issue. The Pharisees would only eat with those who were pure.
And so in Galatians 2, the dispute over Jewish believers eating with Gentile believers was likely a question of eating the communion meal together (Gal. 2:12). Paul saw the need for unity especially crucial here, for it was a question of being covered by the blood of Christ. Jew and Gentile believer both stood equally before the blood of Christ. Both should eat together.
When we celebrate the Lord's Supper as a church, when we "give thanks" in the Eucharist, we both remember what Christ has done and look forward to what he will do. "Christ has died. Christ is risen. Christ will come again." But the Eucharist is more than a remembrance and an anticipation. It is "strength for today," as well as "bright hope for tomorrow."
Communion is a sacrament of renewal and re-empowerment. It is a wonderful time to repent of any sin and trust in God for the power to face another week in his name.
Next Sunday: SA5: Christians vary some in their perspectives on communion.
 The use of grape juice instead of wine rose within Methodism in the late 1800s. A Methodist named Thomas Bramwell Welch invented a process of stopping the fermentation of the juice and his son created the business of Welch's Grape Juice. By the mid-1860s, Methodist churches insisted on using unfermented juice in communion, and most low-church denominations followed suit.
 The Gospels give differing impressions on whether the Last Supper was the actual Passover meal or not. In the Synoptic Gospels of Matthew, Mark, and Luke, we get the impression that the Last Supper was indeed a Passover meal. In John, however, we get the impression that Jesus dies on the cross at about the time that the Passover lambs are being slaughtered for supper than night (e.g., John 18:28; 19:14, 31).
 At Corinth, it is overwhelmingly likely that children participated in the meal. It is not clear from the Didache whether children participated in the eucharistic meal, but it does seem to be a meal, since it mentions being full (10.1).
 We can infer this social status dynamic by what we know about the nature of ancient dining and how even menus were often differentiated on the basis of status at the same meal. See Pliny the Younger, Letters 11.