Today's Gospel picks up from yesterday's, in which Jesus has just embarked in a bit of a huff after rejecting the demand of some Pharisees for a "sign from heaven."
Once in the boat, he warns his disciples about the "leaven of the Pharisees."
The disciples didn't get it. They think he is talking about the fact that they have only one flat loaf of bread with them. And Jesus (evidently still not having recovered from the incident with the Pharisees) barrages them with questions like, "Do you have eyes but no seeing? Ears but no hearing?" And he reminds them of what happened on the occasions when he "broke bread" for the immense crowds and fed 5,000 and then 4,000 people--with loads of bread to spare.
It doesn't really seem like "good news" at first. The Jerome Biblical Commentary helps with that. The JBC notes that the "one bread" in the boat is really Jesus himself, and that the expression "breaking bread" was about as clear as Mark could be to indicate, in story form, that the Eucharist is the "one bread" we need to live on, and that if we have Jesus, we have everything. In all, the Gospel message today could be summed up in the words that are in every Pauline chapel: Do not be afraid; I am with you. From here (the tabernacle) I want to enlighten. Live with a penitent heart.