Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our passover is sacrificed for us. Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth.

1 Corinthians 5:7-8 KJV

We must purge or get rid of the old leaven that corrupts the truth. 

The leaven or yeast is symbolic to sin and unrighteousness in the lives of God’s people. Yeast causes fermentation and so does sin. We have to get rid of the old leaven. Be unleavened, made without the yeast. It’s symbolic to purity. Don’t let the old leaven ruin the whole lump. It only takes a little bit of leaven to ruin the whole lump. And this is how it starts. A little here and a little there. One sin leads to another and, next thing you know, the whole church is affected by what once was a little leaven. Be unleavened and pure. Purge out the sins and things that are not pleasing to God. Just when the thought comes that says you can’t do it. Remember, Jesus gave His life so you can.