Beware of leaven

When we think of leaven, or yeast, most of us probably don’t think we have anything to fear. Leaven is composed for the most part of tiny fungus cells that are harvested and used primarily in the fermentation of alcohol and causing bread to rise. In light of this, it is pretty hard to think of leaven as posing any real threat to us. And yet in Matthew 16:6 Jesus used leaven as an illustration of something we need to be on our guard against: “Watch out and beware of the leaven of the Pharisees and Sadducees.”

It is clear from this statement that Jesus considered leaven as a fitting illustration of a dangerous substance, or he would not have told his disciples to “beware of” it. But obviously the danger of leaven is not in its size, but in the way it works. The power of leaven is that it spreads relatively quickly and ends up affecting the whole of whatever substance it is introduced into. In Matthew 13:33 Jesus compared the kingdom of God to leaven for this very reason – because of its power and potential to spread and affect everything it comes into contact with. We can also see the power of leaven or yeast in 1^st Corinthians 5:6-7: “Don't you know that a little yeast works through the whole batch of dough? Get rid of the old yeast that you may be a new batch without yeast.” Paul was using yeast in this verse to illustrate the way sin encroaches into every area of our life if it is not stopped. He used this same illustration again in Galatians 5:9.

Leaven is in many ways similar to a disease cell in a body that spreads quickly until the entire body is diseased. This is why, in the cases of life-threatening diseases it is so important to discover them early and remove them, so they do not spread throughout the entire body. This same principle can be seen easily in the case of a fast-growing weed. Once such a weed takes root in a garden, for example, it will begins to sap the life out of all the plants around it and, the stronger it gets, the more its root system will spread until eventually one weed can affect an entire garden.

From these simple analogies of disease cells and weeds we can understand why Jesus used the leaven to illustrate something his disciples needed to “beware of.” But the verse that follow make it clear that Jesus’ disciples missed the point he was trying to make; Verse 7 tells us that they thought he was scolding them for not bringing any bread along with them. Jesus told them that he was not talking about literal bread, and verse 12 tells us that they then understood that the “leaven” he was talking about was “the teaching of the Pharisees and Sadducees.”

Understanding that teaching acts like leaven is one of the most powerful revelations we can have. The fact is we are all affected by the teachings of others – not only our contemporaries, but men and women who lived centuries ago, but whose thoughts and ideas continue to exert their influence upon people today. Obviously the greatest example of this is seen in Jesus himself, whose teaching has spread around the world and continues to “leaven” the hearts and minds of people today.

But unfortunately there are many false teachings that have this same “leavening” affect – like the destructive teaching of the Pharisees and Sadducees that Jesus was warning his disciples against. And the primary element of the Pharisees teaching was the mixture of law with grace. This teaching resulted in the belief that circumcision and adherence to the law were both necessary for salvation (Acts 15:1,5), which in turn led to the belief that salvation is a combination of God’s effort and our own. Many people still labor under this false teaching today, and many others like it because they do not heed Jesus’ warning to “beware of the leaven” of such false teaching.

Ultimately the only way to guard ourselves from the “leaven” of false teaching is to always keep ourselves in the Word of God, and following the leading of the Holy Spirit – who will “lead us and guide us into all truth.”