A Warning Against The Leaven Of The Pharisees
As Jesus and His disciples crossed the Sea of Galilee, the Master issued a cryptic warning: "Watch out and beware of the leaven of the Pharisees and Sadducees." The disciples, thinking in physical terms, worried they had forgotten to bring bread. Jesus rebuked their lack of faith, reminding them of the thousands He had fed from a few loaves.
The "leaven" He spoke of was the hypocritical teaching and legalism of the religious elite. Just as a small amount of yeast permeates a whole lump of dough, the false doctrines of the leaders could corrupt the entire nation. He urges His followers to seek the pure truth of the Kingdom instead.
— Matthew 16:6