Before we look at that, we should look at how the previous unit, focusing on understanding Jesus' identity and authority through eating and the breaking of bread, ends. The boundaries of this unit are the two feeding miracles, which are both followed by a story involving water. It is an image of the Exodus, an escape over water and a feeding in the desert, which is why chapter 7 focuses around a true understanding of what purity and holiness is (it is an extension of teaching about the law).
In 8:13-21, Mark closes this unit by showing how the disciples themselves continue to misunderstand Jesus. The passage begins by noting that the disciples had forgotten to bring bread. But they had just collected seven baskets full of bread! They were forgetting to rely on God's abundance in his kingdom. Jesus had just had an interaction with the Pharisees who asked about a sign despite a sign being right in front of them in the form of multiplied loaves and fish! Yet, the disciples, while not asking for a sign, do not understand the sign, and confuse what Jesus' teaching is about.
Jesus taught them to beware of the leaven of the Pharisees. Jesus tied in to the idea of bread, because of what he had just done, to remind the disciples that just a little dose of the false teaching of the Pharisees could go a long way. But the disciples think Jesus is just taking a cheap shot at them for not bringing enough bread! Jesus attributes this to a hard heart and a failure to understand because of that hard heart.
His point is thus: If the disciples had properly understood his identity and authority, they would have perceived the spiritual meaning behind statement about the leaven of the Pharisees. But because of a hard heart, they thought he was talking about something physical.
Do we misunderstand things like this? Are we so focused on ourselves, or on our way of doing things, that we miss the grace that is right in front of us? Do we have the spiritual perception, the spiritual sight, that we need to follow Jesus? This is what Mark is getting at in the next unity (8:22-10:52). The boundaries for this unit are two healing miracles. In both cases, a man is blind and Jesus heals him. But in the first case, the man has to be touched twice by Jesus. The healing doesn't "take" the first time. In the second healing, the healing happens the first time.
There are contrasts between these two healings. In the first one, the man is passive; he is brought to Jesus. He asks for nothing; Jesus takes him and leads him and touches his eyes. His sight returns but it is not clear. Again, he asks for nothing. Jesus takes the lead and touches him again. The man continues to say nothing. But in the second healing, the man is named. He calls out to Jesus. He uses a phrase that indicates a knowledge of Jesus' identity ("Son of David") and authority ("have mercy on me"; i.e., heal me). He was persistent. He asked to receive his sight. And Jesus acknowledged his faith.
What separates these two healings? Why is one passive, low key, and not successful at first, while the second one appears to check all the right boxes? This narrative unit symbolically represents a transition of growth, where someone wrestles with, and comes to know, who Jesus truly is. They were passive at first, but full of faith at the end. But how does this transition happen? We will watch, in chapters 8-10, the disciples struggle three times Jesus' clear articulation of what it means for him to be the Messiah.
He has taught about his identity and authority, and now Jesus ties it together, three times, by describing his upcoming death and resurrection. Each time, the disciples misunderstand what he is talking about. And Jesus goes on to teach about what a true response of faith looks like. In this case, in chapter 8, it is Peter who acknowledges that Jesus is the Messiah they have waited for. Yet, when Jesus teaches that he will go to Jerusalem, be killed, but rise again after three days, Peter appears to become confused. He pulls Jesus aside and lectures him about how that is not the way he envisioned the Messiah going. So Jesus corrects him (8:34-38) -- anyone who wants to follow him must deny himself, pick up a cross, and follow.
The way of Jesus is a way of denial. It is not a way of power, of accumulation, of self-perceived authority. It is a way of sacrifice, of loss, of denying yourself to follow him. Do you see this? Or is it unclear? Are you in need of the second touch of Jesus? Are you dull to understand? Or are you picking up a cross and walking after Jesus?