"The kingdom of heaven is like yeast which a woman having taken, mixed with three measures of wheat flour until the whole of it was permeated by the yeast." —Matthew 13:33
In Matthew 16:6, Jesus says to his disciples, "Be taking heed and be guarding yourselves against the yeast of the Pharisees and Sadducees." By 'yeast' He meant their teaching. Is it possible that in His parable 'yeast' also refers to teaching? Is it also possible that the woman, like in the book of Revelation, refers to a church? If so, is it referencing a specific church or any church? If we look throughout history we can see churches introducing false doctrines that have indeed permeated the whole. We can see even more of it in our modern day, wherein everyone wants their ears tickled. They want their 'religion' to be whatever they want it to be apart from God and His Word. False teachings abound and it seems they have permeated into the hearts of most believers to the point where they refuse to hear sound teaching. It all comes down to feelings and opinions. If the word of truth does not suit my feelings or opinions, then to hell with it. Sadly, the reality is to hell with us. The word of truth will remain true regardless of our acceptance thereof. So beware of churches and teachers who sow false teachings contrary to the Word of God.