If you have ever tried your hand at making bread, you know that the yeast is the leaven that makes the dough rise . A small amount of yeast is all it takes. In Jewish culture, leaven was associated with evil, so when Jesus warned the disciples about the “leaven of the Pharisees and Sadducees,” he was not referring to the bread they might have had but their religious lives. He was pointing out that these two groups had placed their own personal preferences and beliefs ahead of what God had called his people to be. They were so caught up in their own preferences and beliefs that they could not see that God himself was standing right in front of them. More then likely, for them it started small but quickly grew and over took all of their focus.
We tend to get set in our preferences and traditions as Christians. Sometimes we let them take priority over God himself. I know that I have been guilty of living like a Pharisee or Sadducee. For me, the problem is I do not recognize it in myself until someone points it out to me. If I do not check myself and repent, then that preference or tradition will grow in importance just like the leaven of the Pharisees and Sadducees. So here is our wake up call: Check your heart and yourself to see if there are preferences or beliefs that you have elevated above God. If there are, then turn to God and repent. In all that we do, we should seek to elevate God above everything.
A little leaven leavens the whole lump.Galatians 5:9