Are there any scriptures that say that “leaven is sin?”

Someone recently had a great question about Passover.  He asked if there were any scriptures that say that “leaven is sin” because that he thought that “leaven” was simply doctrine, according to Matthew 16:11-12 and 13:33.

Let’s take a look at those scriptures in context:

Matthew 16:11. How is it that you do not understand that it was not about bread that I spoke to you, but that you should be aware of the leaven of the Pharisees and the Sadducees. 12. Then they understood that he did not say to be aware of the leaven of bread, but of the doctrine of the Pharisees and the Sadducees. (AENT)

The verses in Matthew 16 do not mean that actual leaven in BREAD is a bad thing. Rather, that "leaven" in our lives can be bad, because leaven causes things to rise and grow. It permeates everything. Once you allow a sinful thing to enter your mind, your carnal nature tends to go with it and act on it. And after awhile, that particular sin simply becomes "second nature," because you've convinced yourself that God doesn't mind.

Matthew 13:33. He said another parable to them. The Kingdom of Heaven is likened to leaven which a woman took and buried in three measures of flour until it was all leavened.
Matthew 13 obviously refers to GOOD leaven. Once you begin to follow YHWH and His Commands, your whole life begins to take a new direction. (AENT)

The thing is, there is no direct scripture that says leaven represents sin, though at Passover and the Feast of Unleavened Bread it is a sin to eat chomez (leavened bread), Exodus 12:15.  It is also a sin to offer chometz with a sacrifice, Exodus 23:18. However, in Scripture, leaven is often clearly symbolic of sin. Galatians 5:9 tells us that a little leaven leavens the whole lump. Well, as you’ve probably guessed by now, sin works the same way.

Like leaven which permeates the whole lump of dough, sin spreads in a person, a congregation or a nation, eventually overwhelming and bringing all participants into bondage and eventually to death. (There is no such thing as a “little sin.”) Romans 6:23 tell us that “the wages of sin is death,” which, as you know, is YHWH’s judgment for sin, and the reason that Y’shua died.

Back in Deuteronomy 16 we see, "3 You are not to eat any hametz with it; for seven days you are to eat with it matzah, the bread of affliction; for you came out of the land of Egypt in haste. Thus you will remember the day you left the land of Egypt as long as you live. 4 No leaven is to be seen with you anywhere in your territory for seven days.  (CJB)

Other commands regarding the eating of unleavened bread are found in Exodus 12:8; 29:2 and Numbers 9:11. The main reason Passover celebration includes unleavened bread is because YHWH commanded it.  But now you know, “the rest of the story!”