Jesus talked about two kinds of leaven, the leaven of the Pharisees, and the leaven of Herod (Mark 8:15). Jesus frequently teaches in parables and illustrations and here, speaking of leaven, he refers to an infectious spiritual disease that anyone could catch if they were not careful.
The Pharisee Sickness
Symptoms would include hypocrisy (Mark 12:13-15), legalistic interpretation of the Law (Matt. 23:23-24), self-righteousness (Matt. 23:28), haughtiness (Mark 15:31), spiritual pride (Luke 18:11-12), and judgmentalism (Matt. 23:34). This illness is more internal and less outwardly manifest and as such, tends to cause you to hide behind a pretty face while living in a lie. You will be studying the Bible a lot and yet never get anywhere with it. Every line reads like a code of conduct to you. You will be bitching behind closed doors at God because he isn’t honoring your “tithing” or “offerings” or didn’t give you the wife you thought he did, or should have. You like to look good in front of people. You think everyone with a “M.Div” after their name or “Dr.” before it is a god and every peon should bow down to them, or be cast out of the congregation. You boast in everything except in knowing God.
The Herod Sickness
Symptoms would include, immorality, lasciviousness, indifference, apathy, mockery, debauchery, drunkenness, an i-don’t-give-a-f*** attitude, and the like. This illness shows itself plainly, and patients usually exhibit a defensive attitude towards their debauched way of living. They try to assimilate into the Pharisaical mold repeatedly and last a little while…until the shackles and chains rot their souls and they violently bust them to run and hide in the tombs of darkness, at which point no one by the name of “Christian” can talk to you because your trust in them is such that you wouldn’t touch them with a thirty foot pole. Lots of isolation. Lots of suicidal thoughts floating around in the brain (Matt. 2:16; Mark 7:21-23; Eph. 5:18; Eph. 5:4; 1 Peter 4:3; Gal. 5:19-24).
It is best to avoid these kind of people (2 Timothy 3:1-5). Of course we mean those who call themselves brothers and are sick like this (1 Cor. 5:9-13). If you are around them too much you risk the chance of becoming infected (1 Cor. 15:33, Luke 21:34). Come out and touch no unclean dirty thing….
If you are infected with such a disease yourself, take heart, Jesus can heal you (Matt. 12:15; Rev. 3:17-20, John 5:5), even if you’ve had it for 38 years!