TRANSLATION MATTHEW 16:5

The pupils went to the other side but forgot to take bread with them. Then Jesus said to them, “Look carefully and beware of the yeast of the pharisees and the sadducees!”:

They started to debate this amongst themselves, “It’s because we have no bread,” they said.

Noting this, Jesus said,”Why are you debating amongst yourselves, you tiny-trusts, that it’s because you don’t have bread? Do you still not understand? Don’t you remember the five loaves for five thousand and how many baskets you collected? Or the seven loaves for four thousand and how many baskets you collected? How could you fail to understand that I was not speaking to you about bread! Beware of the yeast of the pharisees and the sadducees!”

Then they understood that he had not told them to beware of bread yeast, but of the teaching of the pharisees and sadducees.

Here’s an incident where the interpretation of an event in Jesus life, held by a later generation of believers, who have also fiddled the numbers, is used by Jesus to criticise the faith of his pupils. Yes, when the first Christians meditated on the miraculous feedings they saw them as proof of Jesus kingship over Jew and Gentile, but how could his pupils be expected to think in that way?

Matthew uses the material from Mark, softening his criticism of the pupils but not excising it. He wants to emphasise that a good pupil will reject the teaching of the rabbis in his time.

Because unleavened bread was right for passover, and therefore yeast was ritually cleared from the righteous house for the festival, yeast could be used as a symbol of pervasive wrongness. It is perfectly possible that Jesus used it in this way of teachings he considered wrong and dangerous. The significance of Matthew’s story here may be this: the true king multiplies the true doctrinal food; whereas the pharisees multiply (like yeast) wrong doctrinesIt is quite hard sometimes to enter his mindset.