פירוש על בראשית 25:27

ויגדלו… ויהי עשו AND THEY GREW … AND ESAU WAS — So long as they were young they could not be distinguished by what they did and no one paid much attention to their characters, but when they reached the age of thirteen, one went his way to the houses of learning and the other went his way to the idolatrous temples (Genesis Rabbah 63:10).

יודע ציד, hunting venison and retrieving the animal to serve as food.

ויגדלו הנערים, as soon as they grew up their activities diverged completely from one another, one concentrating on mundane activities, activities which showed immediate profitable results, the other concentrating on the acquisition of knowledge, wisdom, i.e. abstract matters. One was an extrovert, at home in the fields, mountains, etc, whereas the other was an introvert as reflected in the term יושב אהלים.