The following was taken from a book entitled For the Love of God by D.A. Carson.
In Mark’s account of the feeding of the five thousand and of Jesus’ subsequent walk on the water (Mark 6), one finds a small aside that stirs up profitable reflection. As soon as Jesus climbed into the boat in the midst of the raging storm, the wind died down. The disciples, Mark comments, “were completely amazed, for they had not understood about the loaves; their hearts were hardened” (6:51-52).
The first observation is the most obvious; the astonishment of the disciples betrays the dismal fact that they have reflected very little on the spectacular miracle Jesus performed just a few hours earlier. On the face of it, the person who can so control nature as to be able to take a few scraps of food and feed thousands of people can doubtless handle nature well enough to subdue a storm. Yet lest we become too smug in our condemnation of the disciples, we ought to reflect on how easily we forget the Lord’s gracious dealings in our own lives, and are frankly (and shamefacedly) surprised when He intervenes once again.
The second observation lies a little deeper. If Jesus truly is the promised Messiah, if He enjoys the powers He has already displayed, can any responsible disciple think that He is losing control? Can any responsible member of the Twelve imagine that this sort of Messiah could call disciples to Himself, and then lose them all in a boating accident? This is not to suggest that accidents cannot happen to followers of Jesus today. Of course they can–this is a fallen world, and Jesus’ followers are not exempt from all of the tragic and vicious entanglements of its fallenness. But even we must learn in difficult and frightening circumstances to trust God’s wise providence. Here the disciples must surely learn something more–their own peculiar service as the inner core of disciples is so bound up with the ministry of Jesus that it is unthinkable that they could be “accidentally” killed.
And third, one cannot help but reflect on Mark’s conclusion, “their hearts were hardened.” This does not mean they were stupid. Nor does it mean that while their minds were all right, their affections were twisted, as if heart refers to the center of affections alone. In the symbolism of biblical anthropology, heart refers to the seat of human personality, not too far removed from what we mean by mind (although that is perhaps too restrictively cerebral). Their entire orientation was still too restricted, too focused on the immediacy of their fears, too limited by their inability to penetrate to the full mystery of who Jesus is and why He came.
This side of the cross and resurrection, we have still less excuse than they.