Be on your guard against the yeast of the Pharisees and the Sadducees. Then they understood that he was not telling them to guard against the yeast used in bread, but against the teaching of the Pharisees and Sadducees.
Matthew 16:11-12
Just as yeast works its way through bread until the whole thing is proven, the awoken spirit works its way through out the entire body. It works on the character, thoughts, actions, emotions and physical being. It changes a person giving them all the characteristics of the Holy Spirit which is love.
Love is patient, love is kind, it does not envy, it does not boast, it is not proud. It is not rude, it is not self-seeking, it is not easily angered, it keeps no record of wrongs. Love does not delight in evil, but rejoices with the truth. It always protects, always trusts, always hopes, always perseveres.
1 Corinthians 13:4-7