From the First Letter to the Church in Corinth:

Do you not know that a little yeast leavens the whole batch of dough? Clean out the old yeast so that you may be a new batch, as you really are unleavened. For our paschal lamb, Christ, has been sacrificed. Therefore, let us celebrate the festival, not with the old yeast, the yeast of malice and evil, but with the unleavened bread of sincerity and truth.

(From the Daily Office Lectionary – I Corinthians 5:6b-8 (NRSV) – March 18, 2014.)

Saccharomyces Cerevisiae YeastPaul uses the metaphor of yeast in a negative way making it symbolize sin and corruption. In the letter to the Galatians, he uses it in a similar manner in an aside about the few who have “prevented you from obeying the truth,” saying, “A little yeast leavens the whole batch of dough.” (Gal. 5:7,9)

Jesus had used the metaphor in a positive way: “The kingdom of heaven is like yeast that a woman took and mixed in with three measures of flour until all of it was leavened.” (Matt. 13:33; cf. Luke 13:21) But he also warned his disciples to beware “the yeast of the Pharisees.” (Matt. 16:6, Mark 8:5, Luke 12:1)

The point of the metaphor is that a small number of individuals can influence the behavior of a large group. A few years ago, some British researchers demonstrated that this is true even when there is no conscious communication within the group. In a series of experiments groups of people were asked to walk randomly within a large but confined space. A few subjects were given detailed instructions about where to walk. Participants were all instructed to stay at least arms length away from any other person and they were not allowed to communicate with one another.

In every run of the experiment, the instructed subjects ended up being followed by others in the crowd, forming a sort of self-organizing conga line. Iterations with varying numbers of subjects up to 200 demonstrated that it only took 5% of the group being instructed to result in an unconscious group consensus. Despite the fact that participants weren’t allowed to talk or gesture to one another, the group ended up being led by the specially instructed minority.

Just think what a small minority within a church community could do if it were united and made conscious effort to influence the larger group. Think what a vestry, session, or other governing board could do if it put its collective mind to being a “yeast” for good within a congregation. Too often church leaders try to persuade congregations to grow through personal evangelism or to reach out in social ministry or to mature in faith through spiritual discipline without actually demonstrating those behaviors themselves. That hasn’t worked. What works is “leading by example,” which is what the small amount of yeast in a loaf does in a way; it’s what the instructed walkers in the British experiments did.

With just a little bit of care and nurture, a little bit of yeast can grow explosively; the most common yeast used in brewing and baking (Saccharomyces Cerevisiae) can double every 100 minutes! The English word “yeast,” according to the dictionary, derives from the Greek word zestos. The word used in the New Testament for “leaven” (and translated here as “yeast”) is zume. These words have no linguistic link to our modern words “zest” and “zoom,” but it occurs to me this morning that if small leadership groups in our churches got truly zesty for spiritual maturity, for personal evangelism, and for social ministry, there’d be no stopping the church; it would zoom. The church would explode! We need to cultivate a zesty vestry in every congregation!


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Father Funston is the rector of St. Paul’s Episcopal Church, Medina, Ohio.