Leaven, or yeast, can be used for two different teaching analogies. It can represent evil in forms of added religion, complaining, disputing or disobedience where a little in one person can affect the whole Church. On the other hand, we as Christians are supposed to be leaven in the world, infecting the world in a good way for the Kingdom of God. To support this ministry financially, visit: https://www.oneplace.com/donate/640/29