He built a hedge around it, removed its stones, and planted a vine. He built a tower in the middle of it, and constructed a winepress. He waited for it to produce edible grapes, but it produced sour ones instead.

What more can I do for my vineyard beyond what I have already done? When I waited for it to produce edible grapes, why did it produce sour ones instead?

He will eat sour milk and honey, which will help him know how to reject evil and choose what is right.

From the abundance of milk they produce, he will have sour milk for his meals. Indeed, everyone left in the heart of the land will eat sour milk and honey.