In Biblical times, a little bit of leaven was all that was needed to add flavor and give a light texture to a loaf of bread. A little bit hidden in the dough, could make the whole batch of bread rise up. Leaven in the Bible is used in both good ways and bad ways. In this particular teaching, we are looking how a few bad habits in our lives that are not dealt with can ruin our walk. Leaven gets in and it perverts our thinking. We are not to just let things slip, but be diligent and faithful.