Charles Ellicott Commentary Genesis 25:29-30

"And Jacob boiled pottage. And Esau came in from the field, and he was faint. And Esau said to Jacob, Feed me, I pray thee, with that same red [pottage]. For I am faint. Therefore was his name called Edom." — Genesis 25:29-30 (ASV)

Jacob sod pottage. —The diverse occupations of the two youths led, in course of time, to an act fatal to Esau’s character and well-being. Coming home one day weary and fainting with hunger, he found Jacob preparing a pottage of lentils.

No sooner did the savoury smell reach him than he cried out in haste, “Let me swallow, I pray, of the red, this red.” The verb expresses extreme eagerness, and he adds no noun whatever, but points to the steaming dish.

And Jacob, seeing his brother’s greediness and ravenous hunger, refuses to give him food until he has parted with the high and sacred prerogative which made him the inheritor of the Divine promise.

Therefore was his name called Edom. —Esau may have been called Edom, that is, Rufus, the red one, before, but after this act it ceased to be a mere allusive secondary name, and became his ordinary appellation.