Treasury of Scripture Knowledge
Then they perceived that He had not warned them against bread-yeast, but against the teaching of the Pharisees and Sadducees.
and when He admonished them, "See to it, be on your guard against the yeast of the Pharisees and the yeast of Herod,"
Meanwhile the people had come streaming towards Him by tens of thousands, so that they were trampling one another under foot. And now He proceeded to say to His disciples first, "Beware of the yeast of the Pharisees, that is to say, beware of hypocrisy.
1 Corinthians 5:6
It is no good thing--this which you make the ground of your boasting. Do you not know that a little yeast corrupts the whole of the dough?
A little yeast corrupts the whole of the dough.
2 Timothy 2:16
But from irreligious and frivolous talk hold aloof, for those who indulge in it will proceed from bad to worse in impiety,
So the disciples began questioning one another. "Can it be," they said, "that some one has brought Him something to eat?"