Why do we use leavened bread in communion? It might seem odd to some since we use wine. Jesus used real wine at the Last Supper, and since it was a Passover Meal, he would have used unleavened bread at that first Communion. So itís a reasonable question.
First off, leaven does not only represent sin. Sometimes it does and sometimes it doesnít. In 1 Cor. 5, Paul exhorts the Corinthians to get rid of the leaven of malice and wickedness. Likewise, Jesus says to beware of the leaven of the Pharisees, which is hypocrisy. But Jesus also says that the Kingdom is like leaven mixed into three measures of flour, until the whole thing is leavened. Likewise, while some of the sacrifices required unleavened bread, the Peace Offering included leavened bread with the sacrifices of thanksgiving (Lev. 7:10). And while Passover required Israel to get rid of leaven, the Feast of Pentecost required Israel to use leaven (Lev. 23:17).
So putting all of this together, we should understand leaven as representing a principle growth and maturity. And the question is: what are you growing? What are you growing into? Any leaven from Egypt and the Pharisees always needs to be gotten rid of. The leaven of the world needs to be tossed constantly, but the leaven of the Kingdom, the leaven of Pentecost needs to be constantly kept and cultivated and preserved.†
Itís striking that at Pentecost after Jesus ascended to the Father, the Spirit was poured out, and thousands were baptized and converted, and it says that they continued daily in the temple and breaking bread from house to house, eating with gladness and singleness of heart. That phrase ďbreaking breadĒ almost certainly refers to celebrating the Lordís Supper. But since these Jews were doing this from house to house after the Feast of Pentecost, they would have been using leavened bread. And this was perfectly fine since they were celebrating the new Peace Offering, the work of the Spirit, the leaven of the Kingdom filling the whole loaf, until it fills the world.†
So that is why we use leavened bread here. It is not a sin to use unleavened bread, but the question is where are we in the story? Are we primarily trying to get out of Egypt, or have we come to Pentecost, the Feast of the Harvest, the time of the Kingdom where our primary task is to see Christ fill the world with His life? So get rid all of your sinful leaven: your bitterness against your parents, your lust, your envy, and receive the leaven of Christ. Let Him leaven your whole life so that it grows and fills up with His grace.†
So come and welcome, to Jesus Christ.†