Leaven

In the scriptures, leaven represents sin. In the spring before the Feast of Unleaven Bread commences, all Israelites are commanded to remove all leaven from their homes. It's a time of scrubbing, sweeping, and dusting. It's where we get the term 'spring cleaning'. Upon the Passover when Jesus was crucified, the Jews had until sundown to get all of the bodies off of the crosses and into the graves - they were unclean and could not be present during the feast week. Jesus also had to be removed - HE BECAME SIN. To expedite the process, the soldiers were to break the legs of those crucified so that they would die and 'get it over with' - so they could be buried and out of sight. Jesus had already given up His spirit, however, and not one of His bones was broken.

So leaven represents sin.

Mat 16:6
(6) And Jesus said to them, Watch and take heed from the leaven of the Pharisees and Sadducees.

What a strange warning. What is the purpose of such a seemingly cryptic statement? Leaven is yeast - or bacteria. It causes bread to rise. A little bit of leaven will spread into the entire lump of dough. In actuality, even an unleavened lump of dough will soon become leavened if left out in the open because leavening bacteria are in the air. Leaven spreads.
The Pharisees were a smart bunch. Very smart. They knew the scriptures. They practiced them - religiously. They were very religious. The Sadducees were government appointed officials - people of importance. They lorded their positions over the common folk, very often. The spirit of religion makes us feel as though knowledge trumps all else. The spirit of superiority makes us feel divinely elevated above others. Both of these are prideful spirits that work hand in hand to entrap us into a false sense of security. But Jesus never said knowledge was the key, nor position. He said to watch out for the sin that comes from these things.

I know some incredibly smart people, and some very elevated people, and they have no relationship with the God of Heaven. Leaven has done its work. They must now be rescued - and they don't even know they're perishing. That's the trap. They just don't know.

Meanwhile, the rest of us can be on guard against the leaven in our 'houses'. Work to keep it swept out.