The Leaven of Unbelief Text: Mark 8:14-21
Introduction: The Anxieties of Abundance
We live in a world that is drowning in information and starving for wisdom. We have more resources, more technology, and more creature comforts than any generation in human history, and yet we are perhaps the most anxious generation in human history. We are anxious about the economy, anxious about our health, anxious about the culture, and anxious about what tomorrow might bring. This is because anxiety is not fundamentally a problem of scarcity. It is a problem of unbelief. It is a failure to see and to remember.
The disciples in our text today are a perfect picture of this modern malady. They are in the immediate physical presence of the one who had just turned a handful of loaves and fish into a feast for four thousand men, plus women and children. They are sitting in a boat with the incarnate Word of God, the one through whom the entire cosmos was spoken into existence. And what is their chief concern? They forgot to pack lunch. Their bellies are rumbling louder than the truth of God that is sitting three feet away from them.
This is not just a quaint historical anecdote. This is a spiritual diagnosis. It reveals a profound disconnect between what they had seen with their eyes and what they believed in their hearts. And Jesus uses their mundane, material anxiety as the occasion for a dire spiritual warning. He warns them about leaven. Leaven is a powerful biblical metaphor. It is small, it is pervasive, and it works silently from within until it has transformed the entire lump of dough. Jesus is telling them, and us, that there are corrupting worldviews, spiritual poisons, that can infect our thinking and leave us blind, deaf, and forgetful, even when we are in the very boat with Jesus.
The warning is against two kinds of leaven, that of the Pharisees and that of Herod. These represent the two great temptations that have always faced the people of God: the temptation of dead religion and the temptation of godless politics. One corrupts the church from the inside out with hypocrisy and self-righteousness. The other corrupts the world from the outside in with materialism and raw power. But both are leavens of unbelief. Both are man-centered systems that refuse to bow the knee to the Lordship of Jesus Christ. And as we will see, the disciples themselves were not immune to this infection.
The Text
And they had forgotten to take bread, and did not have more than one loaf in the boat with them. And He was giving orders to them, saying, “Watch out! Beware of the leaven of the Pharisees and the leaven of Herod.” And they began to discuss with one another the fact that they had no bread. And Jesus, aware of this, said to them, “Why do you discuss the fact that you have no bread? Do you not yet perceive or understand? Do you have a hardened heart? HAVING EYES, DO YOU NOT SEE? AND HAVING EARS, DO YOU NOT HEAR? And do you not remember, when I broke the five loaves for the five thousand, how many baskets full of broken pieces you picked up?” They said to Him, “Twelve.” “When I broke the seven for the four thousand, how many large baskets full of broken pieces you picked up?” And they said to Him, “Seven.” And He was saying to them, “Do you not yet understand?”
(Mark 8:14-21 LSB)
One Loaf and a Dire Warning (vv. 14-15)
The scene is set with a beautiful and profound irony.
"And they had forgotten to take bread, and did not have more than one loaf in the boat with them." (Mark 8:14)
Mark, under the inspiration of the Holy Spirit, is not just giving us a logistical detail. This is theology. They are worried because they have no bread, and yet they have "one loaf" in the boat. Who is that one loaf? It is Jesus Christ, the Bread of Life who came down from Heaven (John 6:35). Their physical predicament points to their spiritual reality. They were anxious about the absence of earthly bread because they were blind to the presence of the heavenly Bread. Their problem was not a lack of provision, but a lack of perception. They had the ultimate Loaf, and it was more than enough, but their minds were still fixated on the lesser loaves.
Jesus, seeing the state of their hearts, pivots immediately from their physical concern to a far greater spiritual danger.
"And He was giving orders to them, saying, 'Watch out! Beware of the leaven of the Pharisees and the leaven of Herod.'" (Mark 8:15)
This is a command, an urgent order. "Watch out! Beware!" The danger is real and it is subtle. The leaven of the Pharisees is the leaven of religious hypocrisy. It is an external, performance-based righteousness that is meticulous about man-made rules while the heart is full of pride and corruption. It is the spirit that builds fences around God's law and then presents those fences as the pinnacle of holiness. It looks spiritual, it sounds pious, but it is a yeast that puffs up with pride and produces death.
The leaven of Herod is the leaven of secular materialism. Herod was a worldly, pragmatic ruler. He was concerned with power, pleasure, and political stability. His worldview had no room for the transcendent claims of God. The leaven of Herod is the spirit of the age that says religion is fine for your private life, but the real world of politics, business, and culture runs on different principles. It is the belief that man, not God, is the measure of all things. These two leavens seem like opposites, the religious and the secular, but they are two heads of the same beast. Both are systems of unbelief that refuse to submit all of life to the absolute authority of Jesus Christ.
Spiritual Deafness (vv. 16-18)
The disciples' response to this profound warning is almost comically pathetic. It reveals just how deeply infected they already were.
"And they began to discuss with one another the fact that they had no bread." (Mark 8:16)
Jesus is speaking of spiritual kingdoms and corrupting worldviews, and they hear, "He must be upset about the bread." They drag His heavenly teaching down to the most mundane, belly-level concern. This is what materialism does. It makes you deaf to spiritual realities. It interprets everything through the grid of physical appetite and earthly circumstance. Their anxiety about their stomachs made them incapable of hearing what Jesus was actually saying.
Jesus' response is not a gentle correction. It is a series of sharp, diagnostic questions that cut to the heart of their condition.
"And Jesus, aware of this, said to them, 'Why do you discuss the fact that you have no bread? Do you not yet perceive or understand? Do you have a hardened heart? HAVING EYES, DO YOU NOT SEE? AND HAVING EARS, DO YOU NOT HEAR?'" (Mark 8:17-18)
He identifies their problem as a failure to perceive and understand. This is not an intellectual problem. It is a heart problem. "Do you have a hardened heart?" Hardness of heart, in the Bible, is not a lack of emotion. It is a spiritual callousedness, a stubborn refusal to connect God's actions to God's character. It is the condition of seeing the miracles but missing the Messiah. He then quotes from Isaiah and Jeremiah, putting them in the same category as apostate Israel, a people who had all the external privileges of God's presence but were spiritually blind and deaf. This is a severe rebuke. They have functioning eyes and ears, but they are not using them to see and hear what truly matters.
The Cure for Forgetfulness (vv. 18-21)
Having diagnosed the disease, hardness of heart, Jesus now prescribes the cure. And the cure is remembrance.
"And do you not remember, when I broke the five loaves for the five thousand, how many baskets full of broken pieces you picked up?" They said to Him, "Twelve." "When I broke the seven for the four thousand, how many large baskets full of broken pieces you picked up?" And they said to Him, "Seven." (Mark 8:18-20)
Notice what He does. He doesn't give them a new abstract principle. He forces them to recall cold, hard, historical facts. He makes them recite the evidence. "You are worried about one loaf? Let's review the data." He walks them through the feeding of the 5,000, a primarily Jewish crowd, which resulted in twelve baskets of leftovers, a number pointing to the twelve tribes of Israel. Then He walks them through the feeding of the 4,000, a primarily Gentile crowd, which resulted in seven large baskets, a number pointing to completion and the nations. The evidence is overwhelming. He is the God of supernatural abundance for all people, Jew and Gentile alike. He is the Lord of the harvest. Their anxiety in the face of this mountain of evidence is not just foolish; it is insulting.
The antidote to a hard heart is a remembering mind. When you are tempted to anxiety, when you are tempted by the leaven of religious pride or secular materialism, the first thing you must do is remember. Remember what God has done. Rehearse His mighty acts, both in Scripture and in your own life. Our faith is not based on a feeling or a philosophy; it is based on the revealed character and demonstrated actions of the living God.
Jesus concludes with a question that He leaves hanging in the air, a question that echoes down to us today.
"And He was saying to them, 'Do you not yet understand?'" (Mark 8:21)
The question is a call to connect the dots. It is a call to move from merely observing the miracles to understanding the identity of the one performing them. To understand that the one who can create bread out of nothing is the Creator God in the flesh. To understand that if He is in the boat with you, you have everything you need. To understand that the greatest danger is not an empty stomach, but a hard heart infected with the leaven of unbelief.
Conclusion: The Great Physician
This passage is a profound comfort to us, because it shows us that Jesus does not abandon His disciples in their dullness. He stays in the boat with them. He rebukes them sharply, yes, but He does so in order to heal them. It is fascinating to note what happens immediately after this conversation. Jesus arrives at Bethsaida and heals a blind man, and He does so in stages, first seeing men like trees walking, and then seeing clearly. This is a living parable of what was happening to the disciples. Their spiritual eyes were being opened, but it was a process. They were moving from blindness to sight.
We are those disciples. We are in the boat with Jesus, and we are constantly forgetting our lunch money. We are constantly tempted to interpret our lives through the leaven of the Pharisees, trying to earn our standing with God through our own efforts, or through the leaven of Herod, acting as though God has no say over our public and practical lives. We have seen God provide time and again, and yet the next unexpected bill or negative headline sends us into a tailspin of anxiety.
The call to us is the same. Remember. Open your Bibles and rehearse the mighty acts of God. Look to the cross, the ultimate feeding of the multitudes, where the Bread of Life was broken for the sin of the world. Look to the empty tomb, the ultimate proof that our God is the God of impossible abundance, who brings life out of death. When we do this, when we intentionally remember who God is and what He has done, the leaven of unbelief begins to lose its power. Our eyes begin to see, and our ears begin to hear. And we begin to understand that the one Loaf in the boat with us is, and always will be, more than enough.