7They discussed this among themselves and said, "It is because we didn't bring any bread."
8Aware of their discussion, Jesus asked, "You of little faith, why are you talking among yourselves about having no bread? 9Do you still not understand? Don't you remember the five loaves for the five thousand, and how many basketfuls you gathered? 10Or the seven loaves for the four thousand, and how many basketfuls you gathered? 11How is it you don't understand that I was not talking to you about bread? But be on your guard against the yeast of the Pharisees and Sadducees." 12Then they understood that he was not telling them to guard against the yeast used in bread, but against the teaching of the Pharisees and Sadducees." Matthew 16:5-12
My daily Bible reading has taken me much longer than I thought it would, but I've finally reached the gospels. The last few days I read the book of Matthew and half of Mark, and I have to say, I thoroughly enjoyed reading Matthew. In particular, reading it straight through like I did, I caught some of the relational dynamics between Jesus and his disciples. The passage I posted above had me laughing pretty good the other day, because after spending so much time with Jesus and helping him do miracles and receiving many of his teachings, the disciples still didn't quite understand everything. In this particular instance, they had just finished feeding four-thousand people, they'd been part of a huge miracle, and I have to think that they were still in the "afterglow" of the whole thing. And then Jesus tells them to beware the yeast of the Sadducees and Pharisees.
Now, these twelve men know that Jesus talks in parables, and here they are, they'd just been part of something spectacular, and Jesus gives them a warning, and can't you just picture these men sitting in the boat discussing this? And the end result they come up with is that Jesus is annoyed with them because they forgot to bring bread? They just watched him break seven loaves to feed four thousand, and they thought he wanted bread. In the words of Bugs Bunny, what a bunch of maroons! Jesus is incredulous at their interpretation of what he said to them, and I can just see the exasperation on His face as they miss his point entirely.
So what was His point? He was comparing the teachings of the Sadducees and Pharisees to yeast. Yeast is mentioned several times in the Bible to describe teachings and influence- both good and bad. In this case, it was bad influence. Yeast is an incredible organism which multiplies rapidly. It feeds on sugars and expands very quickly. With proper feeding, a single yeast organism can multiply into the thousands in no time at all. By saying that the teachings of the Sadducees and Pharisees were like yeast, he was saying that those bad teachings will spread quickly if not nipped in the bud. All it takes is one person to hear the words of the false teachers and believe them to be right. Then that one person shares that with another and another, and so on. Before you know it, an entire community has taken the bad teachings for gospel, because the yeast was fed and spread.
In the same way, taking those teachings into ourselves can be dangerous. If we open ourselves up to bad influence and negative influences, how long before those influences actually become an influence? We do need to be wary of what we're taking in, we need to be careful of the movies and books and tv shows and websites we open ourselves up to, because the devil will use anything he can to try and scatter his bad yeast. This doesn't mean that we need to lock ourselves in a box, but it does mean that we need to be on guard. If we're watching a tv show, and something doesn't sit right about it, we need to turn it off. If we're watching a movie- even if we're at the theater and we paid for it, we need to walk out and get away from it. We need to be on guard against those things which will cause us to become unclean in the eyes of God.
"Don't you see that whatever enters the mouth goes into the stomach and then out of the body? 18But the things that come out of the mouth come from the heart, and these make a man 'unclean.' 19For out of the heart come evil thoughts, murder, adultery, sexual immorality, theft, false testimony, slander. 20These are what make a man 'unclean'; but eating with unwashed hands does not make him 'unclean.' " Matthew 15:17-20