How is unleavened bread significant in the Bible?

TL;DR:

Leaven is a permeating agent that causes substances, for example bread, to rise. Unleavened bread in the Bible reminds us of the importance of spiritual purity as leaven represents sin.

Unleavened bread is bread that is made without leaven, or yeast. Yeast makes bread rise, so when bread is unleavened, it remains flat and dense. During the Passover, the Israelites ate unleavened bread to commemorate their hasty departure from Egypt, symbolizing purity and readiness for God's deliverance (Exodus 12:17–20; Deuteronomy 16:3). Leaven, symbolizing sin, was prohibited in offerings to the Lord (Leviticus 2:11), emphasizing the need for purity in worship. In the New Testament, leaven represents sin's pervasive influence and corruption (Galatians 5:9), illustrating how sin affects individuals and communities. Removing leaven symbolizes removing sin from one's life, reflecting a call to moral and spiritual purity (1 Corinthians 5:7–8).

from the old testament

The Israelites ate unleavened bread as part of the Passover celebration (Exodus 12:17–20). It was symbolic of the haste with which the Israelites fled Egypt during the Exodus—they left so quickly that the bread did not have time to rise. God instructed them to commemorate the event by eating unleavened bread: "You shall eat no leavened bread with it. Seven days you shall eat it with unleavened bread, the bread of affliction—for you came out of the land of Egypt in haste—that all the days of your life you may remember the day when you came out of the land of Egypt" (Deuteronomy 16:3; cf. Exodus 12:1–13, 33–39).
The Israelites celebrated Passover the year after they came out of Egypt, but some were ceremonially unclean and could not participate. God told Moses they could celebrate at a different time and, again, repeated the commands regarding the Passover, including unleavened bread (Numbers 9:1–14).
In Exodus 29 unleavened bread is used in the consecration of the priests (Exodus 29:2, 32–34).
Leaven was prohibited in offerings made to the Lord (Leviticus 2:11), emphasizing the requirement for purity and the absence of corruption in worship.

from the new testament

Generally speaking, leaven is a symbol of sin and the way sin spreads through its host, affecting the entire organism. Even a small amount of leaven is sufficient to affect an entire lump of dough, and likewise, a little sin will affect an entire church, nation, or the whole of a person's life (Galatians 5:9). Sin starts out small, in the thoughts and in the heart. It then affects the will and the actions, and it eventually leads to spiritual death (James 1:14–15).
Paul warns the Corinthians that "a little leaven leavens the whole lump" and exhorts them to "cleanse out the old leaven that you may be a new lump, as you really are unleavened" (1 Corinthians 5:7).
Jesus warned His disciples against the "leaven if the Pharisees, which is hypocrisy" (Luke 12:1). He also warned them against the "leaven of Herod" (Mark 8:15). In short, these were cautions to not fall into the sins of others and allow those sins to spread.
Interestingly, Jesus uses leaven in a positive light in describing the kingdom of heaven. He said, "The kingdom of heaven is like leaven that a woman took and hid in three measures of flour, till it was all leavened" (Matthew 13:33). Many interpretations can be made from this. The kingdom of God will increase and spread; the gospel goes forth. God works in our hearts and changes us from the inside. That effect is then seen on the outside. Also, while God's rule may not seem readily apparent, Jesus will one day physically reign over the entire earth. The kingdom of God, like yeast, has a transformative effect that may at first seem small and hidden, but it is comprehensive.

implications for today

Once a lump has been leavened, it is not possible to cleanse out the leaven, because it has permeated the dough. Sin cannot be eliminated by human effort or obedience to the law. The law was given to make us aware of sin (Romans 3:20; 7:7). The law was not meant to discourage us, but to encourage us toward Christ, who is the propitiation for our sins. His sacrifice on the cross paid for our sin and made it possible for us to "remove the leaven from the lump." Paul told the Corinthians, "Cleanse out the old leaven that you may be a new lump, as you really are unleavened. For Christ, our Passover lamb, has been sacrificed. Let us therefore celebrate the festival, not with the old leaven, the leaven of malice and evil, but with the unleavened bread of sincerity and truth" (1 Corinthians 5:7–8). Paul is referring to the realities of justification in Christ—we are unleavened and need to cleanse out the leaven (Hebrews 10:10, 14).

The Bible teaches that we do not have the power to remove sin in our own strength. It has permeated us completely, from birth, because—despite future good or evil actions—every person is born in sin simply because we are members of Adam's race. The first Adam brought this death to humanity, but the second Adam (Jesus Christ) brought life (1 Corinthians 15:22). At salvation, the unleavening work begins. It is a work of Christ, not a work that we produce in ourselves (Ephesians 2:8–10). The Holy Spirit indwells believers at salvation and begins working in our lives in a process called sanctification. As the Holy Spirit produces fruit in our lives, reminding us of the truths in Scripture, convicting us of sin, and pointing us to Christ, we become more like Christ, removing more and more of the leaven in our lives (Romans 8:29–30; Ephesians 4; Philippians 2:12–13).

understand

Leaven symbolizes sin and impurity, emphasizing the need for moral and spiritual purity.
Leaven represents sin's ability to spread and corrupt, affecting individuals and communities.
Removing leaven signifies removing sin from one's life, striving for moral integrity and spiritual purity.

reflect

How does the symbolism of eating unleavened bread cause you to turn from sin and turn to Jesus?
How does leaven symbolize sin and its influence in your own life and community?
Reflecting on Paul's exhortation to "cleanse out the old leaven," what steps can you take to remove sin's influence and pursue greater moral and spiritual purity in your daily walk with Christ?

engage

There is both practical and spiritual significance to unleavened bread. In ancient cultures, including among the Egyptians and Mesopotamians, flatbreads made without leaven were commonly eaten. These breads were practical for daily consumption because they could be prepared quickly without the need for rising time, making them convenient for nomadic lifestyles or times of haste, such as during travel or emergencies. This historical context adds an interesting layer to understanding why unleavened bread was eaten by the Israelites during their hasty departure from Egypt and continues to be part of religious observances today.
Considering the pervasive influence of sin as likened to leaven, how can our community better support each other in removing sin's influence and fostering spiritual growth?
Discuss the tension between recognizing our inability to cleanse sin on our own and the transformative work of Christ and the Holy Spirit in sanctification. How does this tension affect our understanding of grace and obedience in our Christian life?