Yeast

“Be careful,” Jesus warned them. “Watch out for the yeast of the Pharisees and that of Herod.”
Mark 8:15


Jesus warns His disciples to watch out for the yeast of the Pharisees and of Herod. What did He mean by that? Well, yeast is a microorganism that causes bread to rise. It’s what makes some bread light and fluffy. Scripture often uses yeast as a metaphor for sin. Just like a small amount of yeast will spread through an entire batch of dough causing it to rise, so too sin’s corrupting influence spreads easily through a community from one person to the next. And, just as yeast puffs bread up, so sinful attitudes and actions tend to puff us up with pride and self-importance.

So, what was this yeast of the Pharisees and of Herod that Jesus was warning the disciples about? Well, in the context of the conversation Jesus just had with the Pharisees in Mark 8, it could be unbelief or the desire for a sign to prove Jesus’ authority. In Matthew’s telling of this story the yeast is identified as the teaching of the Pharisees. (Matthew 16:12). Then again, in a different setting in Luke’s gospel, Jesus identifies the yeast of the Pharisees as hypocrisy. (Luke 12:1). And as far as Herod is concerned, he was guilty of much sin including seeking signs, sexual sin, hunger for power, and worldliness.

So, I think Jesus is warning the disciples that they live in an age that threatens to corrupt them from every side. He is warning them against falling into the errors of the religious hypocrites on the one hand or the worldly, power-hungry politicians on the other. He is reminding them that sinful attitudes and ways of thinking may appear small or insignificant at first, but (like yeast) they spread and grow and puff up and corrupt. So, Jesus is telling the disciples to be careful, to watch themselves, to avoid allowing even the smallest amount of error to be planted in their lives.

You should also beware the corrupting influences of this world. You need to understand that Satan will come at you from all sides. If he can’t get at you one way, he’ll get at you another! You can be corrupted by false preachers just as easily as by unbelievers. Both political and religious influences can lead you astray. And your thinking and your faith can be poisoned from the right just as easily as from the left. So, you have to be on your guard. You have to be careful to reject wrong ideas and sinful attitudes no matter what their source. Otherwise, if you aren’t careful, you will be corrupted by those around you and will become just like the world you are trying to save.