"Yeast" is an image of various false beliefs, religious dogmas, all kinds of false teachings, political, ideological, philosophical ideas, which as a sinful "leaven", are able to "leaven", excite, infect the minds of many people with their lies, seducing them into committing iniquities, leading them away from the path of true knowledge and the execution of the Will of God and so multiplying the sins of man, destroying, destroying, the spirit, soul and body.