"Sourdough" is a symbol of the Laws, the Commandments of God, which are able to transform man's sinful condition into a godly one by following God's Commandments.

"Sourdough" is a symbol of the Word of God, transmitted by the Patriarchs, Prophets, Christ, and Apostles, which excites, induces man to conceive, accept, execute and grow in him righteous thoughts and to multiply righteous deeds.

Negative Meaning.

"Leaven" is an image of various false beliefs, religious dogmas, ideologies, political, philosophical ideas, which can "leaven", infect the minds of many people with their lies, excite the desire to commit sin, to seduce people from the way of true fulfillment of the Will of God, to multiply the iniquity of man.