Q: What’s the difference between the birthright and blessing in the story of Jacob and Esau?
A: The birthright was the special right that belonged to the first-born son to inherit a “double-portion” of his father’s estate. So if a man had two sons, the older would get two-thirds of the estate. This is what Esau gives up for the bowl of stew.
The blessing is much more specific. It was common practice in the Old Testament for fathers to give special blessings to their children/grandchildren when separated from them. With Isaac, though, it’s a little different, because he is (unwittingly) acting as a prophet of God. His blessing is not just a wish, but a statement of how things will actually be. There is a sense in which Isaac was trying to frustrate God’s plan that “the older will serve the younger” with the blessing he THOUGHT he was giving to Esau. But in reality, he was unwittingly confirming the prophecy announced at the twins birth.