When the boys grew up etc. A parable to a myrtle and a thorn bush that were growing up side by side. When they are little, no person could recognize which of them is a myrtle and which is a thorn bush. When the myrtle grew, it gave off a good fragrance, and the thorn bush put out its thorns. So too was it with Esau and Jacob: The whole time they were little, no person would know which of them is righteous and which of them is wicked. When they grew, Esau became a man who knows hunting, that he would hunt living creatures and kill them. But Jacob was a mild man who stayed in camp, that he learned in the study hall of Ever and in the study hall of Shem.
The Myrtle and the Thornbush as Jacob and Esau Grow
Midrash Aggadah, Genesis 25:27