Matthew 13:33
Jesus spoke another parable to them, “The kingdom of heaven is like leaven, which a woman took and hid in three pecks of flour until it was all leavened.”

This is one of Jesus’ many “Kingdom parables” where He compares the Kingdom of God to something else in order to relate truth about how His Kingdom operates. And at first glance, this parable could be interpreted as God’s Kingdom positively affecting the world around it. However, I think if we dig a little deeper we’ll find something different.

In this parable Jesus used the Old Testament understanding of leaven along with an example from his culture to relate a truth about the Kingdom of God.

So what does the Old Testament (and parts of the New Testament) say about leaven? Well, according to the following passages, it is consistently shown in Scripture as exemplifying the presence of impurity or evil.

Exodus 12:15,19
15 ‘Seven days you shall eat unleavened bread, but on the first day you shall remove leaven from your houses; for whoever eats anything leavened from the first day until the seventh day, that person shall be cut off from Israel.
19 ‘Seven days there shall be no leaven found in your houses; for whoever eats what is leavened, that person shall be cut off from the congregation of Israel, whether he is an alien or a native of the land.

Exodus 13:7
“Unleavened bread shall be eaten throughout the seven days; and nothing leavened shall be seen among you, nor shall any leaven be seen among you in all your borders.

Leviticus 2:11
No grain offering, which you bring to the LORD, shall be made with leaven, for you shall not offer up in smoke any leaven or any honey as an offering by fire to the LORD.

Deuteronomy 16:4
“For seven days no leaven shall be seen with you in all your territory, and none of the flesh which you sacrifice on the evening of the first day shall remain overnight until morning.

Matthew 16:6,12
6 And Jesus said to them, “Watch out and beware of the leaven of the Pharisees and Sadducees.”
12 Then they understood that He did not say to beware of the leaven of bread, but of the teaching of the Pharisees and Sadducees.

Mark 8:15
And He was giving orders to them, saying, “Watch out! Beware of the leaven of the Pharisees and the leaven of Herod.”

Luke 12:1
Under these circumstances, after so many thousands of people had gathered together that they were stepping on one another, He began saying to His disciples first of all, “Beware of the leaven of the Pharisees, which is hypocrisy.

1 Corinthians 5:6-9
6 Your boasting is not good Do you not know that a little leaven leavens the whole lump of dough?
7 Clean out the old leaven so that you may be a new lump, just as you are in fact unleavened. For Christ our Passover also has been sacrificed.
8 Therefore let us celebrate the feast, not with old leaven, nor with the leaven of malice and wickedness, but with the unleavened bread of sincerity and truth.
9 I wrote you in my letter not to associate with immoral people;

Galatians 5:9
A little leaven leavens the whole lump of dough.

Although the Jews were allowed to use yeast in their daily baking, under the Mosaic Law it was restricted in bread used in the Feast of Unleavened Bread and the Passover (Exodus 12:8,15-20; Leviticus 23:6-8), and also in offerings placed on the alter (Exodus 23:18;34:25; Leviticus 2:11; 6:17). The only exceptions were the use of yeast in the two wave loaves offered as firstfruits (Leviticus 23:17) and some of the cakes of bread offered with the peace offerings (Leviticus 7:13).

So aside from the two exceptions listed above, yeast was never to be used in anything that was presented to God nor did it have any positive spiritual applications.

Now regarding the example from Jesus’ culture, one of the main characteristics yeast is known for is its ability to work through an entire batch of dough. Because of this it was a common practice for a baker to retain a lump of leavened or fermented dough from a former baking and use it to leaven new dough.

The teaching that yeast in this parable represents the positive influence of the Kingdom of God pervading the world has no Scriptural justification. Nowhere in Scripture does leaven represent good. Likewise, the idea of a converted world at the end of the age is contradicted by the presence of tares among the wheat (Matthew 13:24-30) and bad fish among the good (Matthew 13:47-52) in the kingdom itself.

Although Biblical truth has influence on the world and the power of the Gospel is saving souls, the mixing of leaven into the Kingdom of God is not the method of divine salvation nor the way the Kingdom of God is grown. This parable is then a warning that true doctrine, represented by the flour, would be corrupted by false doctrine. Compare this with the following passages and Jesus’ parable becomes more clear.

1 Timothy 4:1-3
1 But the Spirit explicitly says that in later times some will fall away from the faith, paying attention to deceitful spirits and doctrines of demons,
2 by means of the hypocrisy of liars seared in their own conscience as with a branding iron,
3 men who forbid marriage and advocate abstaining from foods which God has created to be gratefully shared in by those who believe and know the truth.

2 Timothy 2:17-18
17 and their talk will spread like gangrene. Among them are Hymenaeus and Philetus,
18 men who have gone astray from the truth saying that the resurrection has already taken place, and they upset the faith of some.

2 Timothy 4:3-4
3 For the time will come when they will not endure sound doctrine; but wanting to have their ears tickled, they will accumulate for themselves teachers in accordance to their own desires,
4 and will turn away their ears from the truth and will turn aside to myths.

2 Peter 2:1-3
1 But false prophets also arose among the people, just as there will also be  false teachers among you, who will secretly introduce destructive heresies, even denying the Master who bought them, bringing swift destruction upon themselves.
2 Many will follow their sensuality, and because of them the way of the truth will be maligned;
3 and in their greed they will exploit you with false words; their judgment from long ago is not idle, and their destruction is not asleep.

So how much yeast have we been eating? How much false teaching have we been swallowing?

Knowing how leaven works, can we allow even a small portion into our lives? With the warning of Matthew 13:33, I believe it’s every believer’s role to prevent false doctrine from entering the Body of Christ. It’s not a responsibility that we can just shrug off saying, somebody else will take care of it.

Here are three things that each of us, as individuals, can do to help the Body of Christ.

1) We have to be spiritually knowledgeable.
Yeast typically doesn’t look like other grains. Although there are some similarities, a trained baker knows the difference. Likewise, false teachings may have some truth mingled in with it but that doesn’t make it all true. We need to know the difference by staying in God’s Word and by remaining sensitive to His Holy Spirit. Train your spiritual eyes to see the difference.

2) We need to be aware of what’s in front of us.
Yeast doesn’t just hop into the mixing bowl. It must be placed there intentionally. Likewise, we need to pay close attention to what kind of teachings are be taught to us. Luke encourages all of us to not just take somebody at their word whenever they are teaching us (Acts 17:11). We must test the spirits to make sure the source of the teaching is truly from the Lord (1 John 4:1).

3) We need to take a life inventory.
Bakers always know how much of each ingredient they have on hand. Likewise, we need to keep an inventory of our thought life to see if we’re accepting any teaching that doesn’t line up with the Word of God. Ask the Lord to reveal to you any thinking or theology that’s not accurate according to the Bible. Then after He shows you, get it out of your head and thought life before it affects other areas of our life.

If each of us will do our part to guard against the leaven of false teaching, then the Body of Christ will be able to stand strong on the Word of God.