The Disciples Misunderstand Jesus’ Warning About the Leaven of the Pharisees and Herod (Mark 8:14-21)

They had forgotten to bring bread, and they had only one loaf with them in the boat. 15 He enjoined them, “Watch out, guard against the leaven of the Pharisees and the leaven of Herod.” 16 They concluded among themselves that it was because they had no bread. 17 When he became aware of this he said to them, “Why do you conclude that it is because you have no bread? Do you not yet understand or comprehend? Are your hearts hardened? 18 Do you have eyes and not see, ears and not hear? And do you not remember, 19 when I broke the five loaves for the five thousand, how many wicker baskets full of fragments you picked up?” They answered him, “Twelve.” 20 “When I broke the seven loaves for the four thousand, how many full baskets of fragments did you pick up?” They answered [him], “Seven.” 21 He said to them, “Do you still not understand?”

They are crossing the lake by boat, leaving the Pharisees behind, and heading toward the other side of the Sea of Galilee. The disciples have only one loaf of bread in the boat. Jesus uses that ordinary situation to give a serious warning. He tells them to watch out and guard against “the leaven of the Pharisees and the leaven of Herod.” In everyday baking, leaven spreads through the whole batch of dough. In Scripture, that kind of spreading influence can be used as an image for something that quietly permeates and changes a person or a community (1 Cor 5:6-8; Gal 5:9). Luke preserves a similar warning when Jesus says to guard against the leaven of the Pharisees, which he identifies as hypocrisy (Lk 12:1).

The disciples hear Jesus’ words and immediately interpret them on a purely practical level. They assume he is talking about their failure to pack enough bread. Mark shows how easily they miss the point. They are focused on what they lack in their hands, while Jesus is talking about what can take root in their hearts.

Jesus responds by pressing them to think back over what they have already lived through with him. He does not begin by giving them a new sign. He calls them to remember the signs they already received, especially the two feedings. Mark places this conversation right after the Pharisees demand a sign from heaven (Mk 8:11-13). Jesus refuses that demand, and then he turns to his own disciples and exposes a different problem: they have been close to him, they have witnessed and participated in his works, and yet they still struggle to grasp what those works mean.

That is why Jesus’ questions come in a rapid series. He challenges their conclusion about bread. He asks why they still do not understand or comprehend. He names the deeper issue with a blunt phrase: “Are your hearts hardened?” In the Old Testament, a hardened heart describes resistance to God’s actions, even when those actions are plain (Ex 10:1; 14:18). The prophets also rebuke God’s people for having eyes and ears but failing to see and hear what the Lord has done (cf. Isa 6:9-10; Jer 5:21; Ez 12:2). Mark’s wording places the disciples uncomfortably close to that tradition of spiritual dullness. They are not outsiders to Jesus’ ministry, but they are still slow to perceive.

Jesus then asks about the first feeding: five loaves for five thousand, and the number of baskets gathered afterward. They answer correctly: twelve. He asks about the second feeding: seven loaves for four thousand, and the baskets gathered afterward. They answer correctly again: seven. The problem is not that they cannot recall the numbers. The problem is that they can remember details without drawing the obvious conclusion. If Jesus has already provided abundant bread in the wilderness twice, the presence of only one loaf in the boat is not a crisis. Their anxiety about food shows that they have not yet learned to read his actions with a deeper understanding.

Mark has already signaled this weakness. After the earlier miracle on the sea, he says the disciples did not understand about the loaves, and their hearts were hardened (Mk 6:52). This episode echoes that earlier diagnosis and intensifies it. The disciples are not being asked only to believe that Jesus can do wonders. They are being trained to recognize what kind of authority Jesus carries and what kind of kingdom he is enacting. Mark presents this as a continuing challenge for Jesus’ followers, who can remember the facts about him yet still struggle to grasp what those facts demand in each believer’s life.

That helps clarify why Jesus pairs the Pharisees and Herod in the same warning. In Mark, the Pharisees repeatedly press Jesus, testing him and challenging his authority. Herod appears as a ruler who protects his position and reacts to threats, even at the cost of John the Baptist’s life (Mk 6:14-29). In different ways, both represent forms of influence that work from within: a posture that resists God’s action, manipulates what is holy, or uses power to protect himself rather than to serve God’s purposes. Jesus warns his disciples because the ‘leaven’ he names can spread within a person. His point is that the disciples must not absorb the Pharisees’ and Herod’s way of responding to him.

The “leaven” warning, then, is not mainly about bread. It is about what shapes perception. The disciples are physically with Jesus, but they are still learning how to see. Their misunderstanding is part of a larger pattern in this section of Mark. 

At the end of the scene, Jesus asks one final question: “Do you still not understand?” Mark leaves that hanging. The disciples are not rejected, but their lack of understanding is made clear. They have heard Jesus’ warning, they have seen his provision, and they can recite the facts. What they still lack is the spiritual perception that connects those facts to the truth about Jesus’ mission and the kind of life he is forming in his followers through his teaching.

Lord Jesus, give me a clear mind and a faithful heart. Help me to remember what you have done and to understand what it means. Guard me from influences that dull faith, twist your truth, or turn power into self-interest. Teach me to see your works rightly and to follow you with trust. Amen.

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Sources and References

• The Holy Bible, New American Bible, Revised Edition (NABRE), Mk 8:14-21.
• Ignatius Catholic Study Bible: New Testament, Mark, p. 79.
• New Jerome Biblical Commentary (1990), Mark, pp. 613-614, para. 52.
• Navarre Bible: The Gospels and Acts, Mark, p. 191.
• Paulist Biblical Commentary (2018), Mark, p. 997.
• The Jerome Biblical Commentary for the Twenty-First Century (2020), Mark, pp. 1262-1263.