There are several comical moments that we come across as we read through the Bible (see Judges 3:24-25, Esther 5:9-7:10 and 2 Kings 2:23-24 if you're in doubt!), and Mark 8:16 has to be up there with the best of them. Here we find disciples picking up on the word 'leaven' in something that Jesus has said, and concluding that they're in trouble for forgetting to bring bread with them. One would have thought that having now witnessed Jesus feeding a combined total of 9000 men with 19 loaves of bread, they might have cottoned on to the fact that lack of food isn't an obstacle to Jesus! (a point that Jesus makes to them in v18-20).

But the sad fact of the matter is that they've still not understood who Jesus is—and to be honest, we're not particularly surprised about that fact either. The evidence has been there all the way through Mark 4-8 (see 4:13, 4:41, 6:51-52, 7:18). Consistently, in the face of overwhelming evidence, the disciples have not recognised who Jesus is; God's king, the shepherd of Israel, who is none other than God himself (6:30-52).

Shockingly, Jesus verdict on the disciples is that they are no different from the Pharisees or the Herodians; they have hard-hearts. That is to say, the sinful condition of the human heart that Jesus described in 7:1-23 is true of everyone alike, and prevents people from understanding who Jesus is.

Nevertheless, we remember that when Jesus called the twelve to himself in Mark 3:13-19, he was calling to himself a new people, a new Israel. So if this new Israel has the same problem as the old Israel, what's the difference? And how come the disciples are in, while the Pharisees, who have exactly the same problem, aren't?

Before we can answer those questions, we need to deal with another big surprise—by the end of 8:30, the disciples have understood who Jesus is. What explains this sudden grasping of Jesus' identity, when just a few verses earlier the disciples seem to be so clueless?

The only explanation can be that Mark has included this story of Jesus' healing of a blind man in between these two events for a reason. Just as Jesus miraculously opens this man's eyes, so he is able to miraculously open the disciples' eyes (Mark 8:18) to perceive who he is. The disciples hadn't worked it out for themselves—Jesus had given them understanding!

So here's the key question that the whole of Mark 4–8 has been building up to. What's the difference between a follower of Jesus and someone who rejects Jesus?

The answer: only grace.