The disciples had forgotten to bring bread,
and they had only one loaf with them in the boat.
Jesus enjoined them, “Watch out,
guard against the leaven of the Pharisees
and the leaven of Herod.”
They concluded among themselves that
it was because they had no bread.
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?
Do you have eyes and not see, ears and not hear?
And do you not remember,
when I broke the five loaves for the five thousand,
how many wicker baskets full of fragments you picked up?”
They answered him, “Twelve.”
“When I broke the seven loaves for the four thousand,
how many full baskets of fragments did you pick up?”
They answered him, “Seven.”
He said to them, “Do you still not understand?”
8:14 Mark begins by noting the seemingly irrelevant detail that the disciples had forgotten to bring bread and had only one loaf with them. On one level, this simply means that they have failed to replenish their food supplies. But the two miraculous feedings and ensuing discussions have prepared us to understand: What is the real “one loaf” (literally, “one bread”) with them in the boat? It is Jesus! Mark clarifies in verse 16 that actually they have “no bread”—no earthly bread, that is.
8:15 But the disciples do not yet understand, so Jesus takes the opportunity for a teaching moment. He admonishes them with a mini parable: guard against the leaven of the Pharisees and of Herod. Leaven, or yeast, is used to make dough rise; a tiny amount is all that is needed to permeate the whole batch. Jesus is referring to a spiritual leaven—the hypocrisy, insincerity, and ill will that the Pharisees (3:6; 7:5–13; 8:11–13) and Herod and his supporters (3:6; 6:14–29) have shown toward him. This admonition shows that even his disciples are not immune to such faults. As Jews knew well, all leaven had to be cleared out of their homes during Passover, commemorating their flight from Egypt in haste, with no time to let dough rise (Exod 12:14–20). Mark’s first readers might have noticed an allusion to Jesus, the true Passover Lamb (see 1 Cor 5:7).
8:16–18 But all this goes over the heads of the disciples, who remain on an earthly level. With remarkable cluelessness, they conclude that Jesus is scolding them for having forgotten to bring bread. After twice seeing him bring overflowing abundance out of a few loaves and fish, they are still worried about where they will get their next meal. In a series of seven questions, Jesus reproves them for their spiritual blindness. The emphasis on understand, comprehend, see, hear, and remember accents the mental effort required to grasp the hidden meaning of what they have witnessed. The most stinging question is in verse 17: Are your hearts hardened? Only in Mark (here and in 6:52) is hardness of heart attributed even to the disciples. Jesus echoes the prophetic indictment of Israel: Do you have eyes and not see, ears and not hear? (Jer 5:21; see Isa 6:9–10; 43:8; Ezek 12:2). Having seen so many wondrous acts of God on their behalf, Israel had failed to recognize what those deeds revealed about God himself. But although human beings are at fault for this spiritual blindness, ultimately only God can provide the solution. The breakthrough in understanding will come by a gift of God (see Deut 29:3), as will happen finally at Jesus’ passion and resurrection.
8:19–21 The emphasis on the number of wicker baskets full of fragments left after the feeding miracles seems curious. What is the significance of these numbers? On one level they remind the disciples of Jesus’ superabundant provision of nourishment for multitudes of people, a provision that will continue through the whole history of the Church. But symbolically they seem to refer to the nations who hear the gospel and are gathered into the Church: the twelve tribes of Israel and the seven nations representing the Gentiles, who once were excluded from God’s people but now share in the “children’s bread” (7:28; see Eph 2:11–13; 1 Pet 2:10). Together, both Jews and Gentiles will partake of the “one loaf” that is Jesus. This is the mystery that Jesus is urging his disciples to understand.
Friends, a few days ago, we read about Jesus’ multiplication of the loaves and fishes. Then in today’s Gospel, which takes place just a few verses later, the disciples ask again about bread. But Jesus turns their attention elsewhere.
He warns them about “the leaven of the Pharisees and the leaven of Herod.” What does he mean by this? He’s referring to the contagious and dangerous “food” offered by these leaders. For example, the Pharisees knew the law of God but used it to oppress people rather than liberate them. They could point out, with great accuracy and articulation, the wicked things that people were doing, in order to bring those people down, to humiliate them.
Beware that sort of food, Jesus suggests. Instead, seek the true bread of heaven which multiplies grace upon grace.
– Bishop Robert Barron
May the virtues of faith, hope, and love go with you today – DV.
 Mary Healy, The Gospel of Mark, Catholic Commentary on Sacred Scripture (Grand Rapids, MI: Baker Academic, 2008), 154–155.