The Bible tells us that the Israelites were to eat only unleavened bread every year during Passover as a commemoration of the Exodus from Egyptian bondage. Since the children of Israel left Egypt hastily, they did not have time for the bread to rise, so it was made on that very first Passover without leaven, also known as yeast. In describing this bread and why it was eaten, the Bible informs us of the following: "Do not eat it with bread made with yeast, but for seven days eat unleavened bread, the bread of affliction, because you left Egypt in haste—so that all the days of your life you may remember the time of your departure from Egypt" (Deuteronomy 16:3). Further commands regarding the eating of unleavened bread are found in Exodus 12:8; 29:2; and Numbers 9:11. To this day, in Jewish homes, the Passover celebration includes unleavened bread.
According to the Hebrew lexicon, the term unleavened bread is derived from the word matzoh, which means "bread or cake without leaven." The lexicon also states that matzoh is in turn derived from a word which means "to drain out or suck." In referring to this second Hebrew word, the lexicon states, "In the sense of greedily devouring for sweetness." So it is quite possible that unleavened bread, while it may have been heavy and flat, may also have been sweet to the taste.
In the Bible, leaven is almost always symbolic of sin. Like leaven that permeates the whole lump of dough, sin will spread in a person, a church, or a nation, eventually overwhelming and bringing its participants into its bondage and eventually to death (Galatians 5:9). Romans 6:23 tell us that “the wages of sin is death,” which is God’s judgment for sin, and this is the reason that Christ died—to provide a way out of this judgment for sin if man will repent of his sins, accept Christ as his Passover sacrifice, and have his heart changed so that he can conform his life to what God commands.