It’s good Jesus explained this and His explanation was recorded because some Christians would be obstaining from yeast and condemning those who don’t and calling those whose view of scripture is not wooden unbelievers. There would be debates and arguments and people without a wooden view would say, “What about the fish and loaves, perhaps He meant yeast represented the sin in the form of the teaching of the Pharisees not the literal bread they ate.” The ones with a more wooden view would say “The fish and loaves was before Acts” or “The multiplied bread was unlevened. If Jesus said stay away from yeast that’s what He said, it’s the bible and I believe it…” and on and on… 😄
And Jesus said to them, “Watch out and beware of the leaven of the Pharisees and Sadducees.” They began to discuss this among themselves, saying, ” He said that because we did not bring any bread.” But Jesus, aware of this, said, “You men of little faith, why do you discuss among yourselves that you have no bread? Do you not yet understand or remember the five loaves of the five thousand, and how many baskets full you picked up? Or the seven loaves of the four thousand, and how many large baskets full you picked up? How is it that you do not understand that I did not speak to you concerning bread? But beware of the leaven of the Pharisees and Sadducees.” Then they understood that He did not say to beware of the leaven of bread, but of the teaching of the Pharisees and Sadducees.
Matthew 16:6-12 NASB