Matthew 16:6 Then Jesus said to them, Take heed and beware of the leaven of the Pharisees and of the Sadducees.

Leaven is a symbol or a type of prideful, puffed-up sin.  The Pharisees had great pride in their own righteousness.  They were the intellectual conservatives of their day.

The Sadducees were the intellectual liberals of the day.  They didn't beleive in such things as heaven, hell, angels, or spirits.

Many of the religious people of today have great pride in their own righteousness.  The better the orator, the harder it is not to have pride.  We all must realize that being born again is the first step.  Growing to fullness is the real goal.  Every blessing that God has given is needed for us to move forward to receive and appropriate the glory that God has planned to reveal in his saints.  We will be satisfied when we awake in His likeness.