When I was a sophomore in college, I lived in a dormitory suite with nine other guys: six bedrooms, two sitting rooms, and a large locker-room style bathroom. About mid-way through the first semester, one of our number, a 3rd-year biochemistry major, suggested that set up a small brewery in one of the sitting rooms. We all read up on how to make beer and thought it was a great idea; so we helped him do it. It takes three to four weeks to make a batch of beer, so over the next few months we made quite a bit of beer.

Then, late in the spring semester, one of our roommates had a chance to get some yeast from a famous California champagne producer, so we thought we’d use it in our beer. We thought we’d be super-cool making beer with champagne yeast and our beer would be magnificent; we weren’t and it wasn’t. In fact, it was downright awful.

It turns out that not all yeasts are the same!

In today’s gospel lesson Matthew’s Jesus offers five short parables of the kingdom in rapid succession one of which is this: “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.”[1] In fact, Jesus doesn’t actually say “yeast’! What he says is “The kingdom of heaven is like zume” which is a word Greek-speaking Jews like Matthew used to describe chametz, the fermented grain or leaven, that is to be removed from one’s home during Passover[2] and which is never, ever to be included in any burnt offering or sacrifice made to God.[3]

Usually in the Scriptures, in fact every other place in the Old Testament or the New that anyone uses chametz or zume as an analogy, it represents evil, corruption, or bitterness. For example, in Psalm 73 the poet says:

When my mind became embittered,
I was sorely wounded in my heart.
I was stupid and had no understanding;
I was like a brute beast in your presence.[4]

That first line is “When my mind became chametz” … “when my mind become leavened.” In his letter to the Galatians, where Paul is warning them about false teachings which would “prevent them from obeying the truth,” he writes: “A little yeast” — a little zume –– “leavens the whole batch of dough.”[5]

Back in Biblical times folks didn’t know that yeast was what made the leaven do its thing, but now we do. I suppose that’s why modern translators go the further step and render these words as “yeast.” However, I believe we should think of this stuff, this little bit of yeasty dough added to a new batch of bread, as sourdough starter because that’s what it really is.

Each time a baker would make a batch of bread, she would save a bit back, and keep it moist and fed until the next batch. And every brewer would do the same, from every batch of beer, a small amount of the fermenting wort would be saved to start the next batch. And every spring they would throw it out, destroy it, because it is corrupt, unclean, and offensive to God. As one commentary on the Book of Leviticus says, chametz is “the arch-symbol of fermentation, deterioration, and death and, hence, taboo on the altar of blessing and life.”[6]

And here is Jesus saying that God’s kingdom, the kingdom of heaven, is like this stuff, like chametz, like unclean leaven! Go figure! Jesus is, once again, standing expectation on its head and saying that God’s kingdom is like sourdough starter! I can just hear the crowd on the shore asking, “What is he talking about?”

I think Jesus is saying, as I learned in college, that not all yeasts are the same. Some yeasts are good and some yeasts are bad, just like people; some are good and some are bad. And I want to suggest to you that this metaphor, of all the parables we have heard the last couple of weeks and today, speaks a great deal to our world and our role within it.

A few years ago, the Christian writer Philip Yancey wrote an essay in the Washington Post in which he confessed to suffering an existential crisis.[7] It was simply this, that he wasn’t reading enough, or rather than he wasn’t doing the right kind of reading. He began with these words:

I am going through a personal crisis. I used to love reading. I am writing this blog in my office, surrounded by 27 tall bookcases laden with 5,000 books. Over the years I have read them, marked them up, and recorded the annotations in a computer database for potential references in my writing. To a large degree, they have formed my professional and spiritual life.

“I used to read three books a week,” he said. But these days that is practically impossible for him, as it may be for many of us. “The Internet and social media have trained [our] brain[s] to read a paragraph or two, and then start looking around.” As writer Sven Birkerts accurately predicted in 1994, “We will be swimming in impulses and data—the microchip will make us offers that will be very hard to refuse.”[8] And beyond Yancey’s complaint of shallowness and brevity, the internet and social media are rife with disinformation, both that which is simply mistaken and that which is willfully, malignantly intentional.[9]

When you mix your sourdough starter into a batch of dough or your beer starter into a new batch of wort, you want the yeast in that starter to do the job. You have a pretty good idea what the end product will taste like. Some wild yeasts or other microorganisms might get in there and contribute some distinctive notes or flavors to the batch, which is OK. In fact, sometimes it’s better than OK. But you don’t want those foreign organisms to take over. It’s not often a problem with bread, but with beer some strains of yeast, as well as molds or bacteria, can ruin it, give it a bad taste or smell, like old gym socks or sewage. When that happens, the batch is referred to as “infected,” and there’s practically no way to cure an infected beer. You have to throw it out, sterilize your equipment, possibly discard some of it, and start over.

A malignancy has infected our society producing misinformation, propaganda, deception, and conspiracy theories like the bad odors and flavors of a foreign organism infecting a batch of beer, but I don’t believe that we have to throw out our society, discard our institutions, and start over — at least, I have hope that we don’t. After all, we are the yeast of the kingdom of heaven, and yeast competes!

“Yeast,” says a recent report from the University of Tokyo, “is not [a] simple single-celled microorganism;” it is “a competitive killer.”[10] When yeast competes for resources, it releases compounds into its environment which can inhibit or even kill competing microorganisms including other yeasts. And then it grows, rapidly. 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 –– the kind of yeast that would have been in that lump of chametz Jesus was talking about –– can double every 100 minutes! Starting with a single cell, “after 24 hours there are about 16,000 cells, and after 48 hours we are counting 268 million cells. Before 3 days are gone there are on the order of a trillion yeast cells.”[11]

My friend Matt Skinner who teaches New Testament at Luther Seminary in St. Paul, Minnesota, says that Jesus’ parables “punctuate the absurdity of it all” and invite us “into a future that could get weird.”[12] Recently, I read a sermon about the Parable of the Talents in which the preacher said, “If we want to be faithful Christian disciples, then we must live into the words and ways of Jesus.”[13] So how do we live into being sourdough starter, how do we live into the weird future of being competitive yeast?

I think a clue comes from Yancey’s essay. We have to read, we have to model reading for others, and we have to encourage those others to read for themselves! And I know that here, in this congregation, I am preaching to the choir, so please consider this sermon to be cheerleading and rallying rather than admonition or reproof. Fostering what used to be called, without any political implication, a liberal education, particularly through a wide ranging program of reading, is, I believe, part of the job of institutions like this one, of colleges, of churches, and of Christian communities, but we don’t seem to talk about that much anymore.

The other yeast seems to be winning in this regard! There are celebrities and “influencers” who brag that they haven’t read a book in years. The average American male spends fewer than 15 minutes a day reading (that’s only about 90 hours a year); the average American woman spends just under 20 minutes a day doing so (that’s around 120 hours a year).[14] On the other hand, the average American currently spends 815 hours annually on social media[15] and 1,692 hours watching TV.[16]

Once a year, and some years not even then if the church calendar doesn’t work out just right, we pray on one Sunday just before Advent starts that God will “grant us [the opportunity and ability] to hear…, read, mark, learn, and inwardly digest” one book in particular.[17] We need to openly, unashamedly, and frankly unsubtlely model and encourage that sort of practice with regard to all sorts of books and journals. Modern Christians have to do, and must encourage and empower others to do, the “hard work of focused concentration on reading”[18] from a variety of sources. This is what is needed to build up our store of resources to combat the propaganda and disinformation that comes from the other kind of yeast. We have to build communities of our sort of yeast: book clubs, literary societies, reading circles, whatever you want to call them.

The sort of reading we must do and must encourage is what Birkerts calls “vertical” reading, the deep, devotional process of spending time with literature through which “we slip out of our customary time orientation, marked by distractedness and surficiality, into the realm of duration.”[19] The job of the yeast of the kingdom of heaven is to develop wandering, creative minds filled with the products of such deep reading, minds prepared to combat the superficial demands of what Yancey called “the tyranny of the urgent” and to compete with the propaganda and misinformation produced by the other sort of yeast.

We should not be focused on a quick or immediate result, however. “Lasting changes occur incrementally and are driven by persistence.… The Taoist maxim that the ‘destination is the journey’ applies here. Persistence is the goal, but it is also the means of change.”[20] The one who endures, promised Jesus, is the one who will be saved.[21]

As Dr. Micah Naziri observed in his dissertation on Jewish-Muslim reconciliation efforts:

[T]here is no goal … to reach, no mile marker for social progress and change, besides perseverance. The journey is the goal. By continuing the journey, persistence is shown and societal change will eventually be catalyzed by this in the same manner that dough is transformed by the mere presence of yeast within it in a heated environment.[22]

At the end of today’s gospel lesson, Jesus says, “Therefore, every scribe who has been trained for the kingdom of heaven is like the master of a household who brings out of his treasure what is new and what is old.”[23] To be the yeast of the kingdom of heaven, we must be trained like those scribes. We must read deeply, experience life, do the hard work of becoming Christian leaders who can mine the wisdom of the ages, both the old and the new, both the religious and the secular, and proclaim by word and example the Good News to the people around us. This requires study; it requires imagination and creativity; it requires deep reading and contemplation. But in the end, at the heart of it all, there is great reward.

My college roommates and I ultimately failed at beer making, at least at making beer with champagne yeast, and we had to discard our equipment and give up that enterprise. But the reading we did and the experience we gained? Well… when Jesus talks about yeast, about the good yeast of the kingdom and, elsewhere, about the bad leaven of the Pharisees, I have a pretty good idea what he’s talking about. He’s not really talking about yeast; he’s talking about us.


This homily was offered by the Rev. Dr. C. Eric Funston on the Ninth Sunday after Pentecost, July 30, 2023, to the people of Harcourt Parish, Gambier, Ohio, where Fr. Funston was supply preacher during that parish’s rector’s sabbatical.

The lessons were from Proper 12A (Track 1) of the Revised Common Lectionary: Genesis 29:15-28; Psalm 105:1-11,45b; Romans 8:26-39; and St. Matthew 13:31-33,44-52. These lessons can be read at The Lectionary Page.)

The illustration is a dish of sourdough starter.


Click on footnote numbers to link back to associated text.

[1] Matthew 13:33 (NRSV)

[2] Exodus 12:15

[3] Exodus 34:35; Leviticus 2:11

[4] Psalm 73:21-22 (BCP Version)

[5] Galatians 5:7,9 (NRSV)

[6] Harper Collins Study Bible, notes on Leviticus 2:11 (HarperOne, San Francisco:2006)

[7] Philip Yancey, The Death of Reading Is Threatening the Soul, Washington Post, July 21, 2017, accessed 27 July 2023

[8] Sven Birkerts, The Gutenberg Elegies: The Fate of Reading in an Electronic Age, quoted in Mairead Small Staid, Reading in the Age of Constant Distraction, The Paris Review, February 8, 2019, accessed 29 July 2023

[9] See, for example, Jill Lepore, Children of Zorin, The Last Archive podcast, June 10, 2021, runtime 48:32

[10] University of Tokyo, Yeast Is a Competitive Killer – Scientists Discover a New Venomous Phenomenon, SciTechDaily, December 17, 2022, accessed 28 July 2023

[11] Martin Lersch, Take the guessing out of baking: Calculate the right amount of yeast, Khymos, November 15, 2020, accessed 29 July 2023

[12] Matt Skinner, Hide Away, Working Preacher, July 23, 2017, accessed 29 July 2023

[13] Tim Ehrhardt, A Parable about Faithfulness (Luke 19:11-27), TimEhrhardt.com, November 2, 2022, accessed 29 July 2023

[14] Dimitrije Curcic, Time Spent Reading in the US, WordsRated, May 26, 2023, accessed 29 July 2023

[15] Josh Howarth, Worldwide Daily Social Media Usage (New 2023 Data), Exploding Data, April 10, 2023, accessed 29 July 2023

[16] Rebecca Lake, Television Statistics: 23 Mind-Numbing Facts to Watch, CreditDonkey, February 26, 2023, accessed 29 July 2023

[17] Collect for Proper 28, The Book of Common Prayer 1979, page 236

[18] Yancey, op. cit.

[19] Quoted in Staid, op. cit.

[20] Micah B.D.C. Naziri, Persistence of Jewish-Muslim Reconciliatory Activism in the Face of Threats and “Terrorism” (Real and Perceived) From All Sides (Antioch University, Los Angeles:2020), page 222

[21] Matthew 10:22, 24:13

[22] Naziri, op. cit., page 223

[23] Matthew 13:52 (NRSV)