Those who make homemade bread understand the power of leaven. Just a pinch of leaven in a large lump of dough permeates the entire lump, causing the bread to rise when baked. In these cases, leaven is wonderful! But the nature of leaven was used to illustrate the power and influence of sin from the earliest days in Israel’s history.
With the institution and observance of the Passover came the feast of unleavened bread (Ex 12). For seven days following the Passover, no leavened bread was to be eaten and no leaven could be found in one’s house under the penalty of death.
Paul further illustrated the defiling nature of sin using leaven in 1 Corinthians 5, where the church had prided herself on her egalitarian attitude toward a brother in a sin so egregious that it was not even known among the Gentiles (and in Corinth, that was really saying something!).
Mark’s account of the leaven of the Pharisees is the only one that does not identify the specific concerns or identity of the leaven. Matthew’s account and Luke’s account speak to the doctrine and hypocrisy of the Pharisees.
But Mark also includes the leaven of Herod. There is no known doctrine associated with the Herodians, as they were a political party; so this may be a warning to the disciples not to become entangled in political affairs. The Jews had entangled themselves with the Herodians, who were Idumeans, who in turn were inextricably intertwined with Rome.
There is certainly a lesson for the church today. In times long since gone, America’s political parties both defended the basic principles of morality: the sanctity of marriage, the sanctity of human life, etc. The differences between the parties were centered on the best way to keep America safe and her citizens prosperous.
But those days are long gone. Now the political arena is filled with battles over matters of morality. Christians should support and uphold those who espouse the basic principles of godliness, but churches need to keep themselves separated from the powers that be and avoid any of the pitfalls inherent in politics and the political process.