Sourdough bread became popular during the California Gold Rush of the mid-1800s. In the 1890s, it was a favorite during the great Gold Rush in Alaska. Prospectors would carry with them a small portion of sourdough mix that contained a natural yeast. It could then be used as a starter to make more of their favorite sourdough bread.
In the Bible, though, yeast or leaven can have a negative connotation. For example, in the New Testament, “leaven” is often referred to as a corrupting influence. This is why Jesus said: “Beware of the leaven of the Pharisees, which is hypocrisy” (Luke 12:1).
Hypocrites put on a show of righteousness while hiding sinful thoughts and behavior. Christ warned His disciples and us that secret sins will someday be exposed to full disclosure. He said, “There is nothing covered that will not be revealed, nor hidden that will not be known” (v.2). Because of this, we are to reverentially fear God, to ask for His grace to forsake any sin, and to grow as authentic believers.
Yeast may be a blessing in the bakery, but it can also remind us to guard against the permeating influence of sin in our hearts.