When you add a small amount of leaven to a lump of dough, it leavens the whole lump and the dough rises overnight. The Bible tells us in Corinthians 5:6 that a little leaven leavens the whole lump of dough in order to let us realize that the misdoings of a few can lead many people to the way of untruth. Likewise, we must try to cast off hatred, anger, and laziness in our hearts even though they do not look very serious. This is because they will become serious over time and finally cause our spirits, souls, and bodies to become lifeless if we let them remain there. Therefore, when you spot evil in your heart, get rid of it immediately. It is the wisdom of life to get rid of even a tiny flaw from your heart if it is against the Word of God.