Genesis 25:27

And the boys grew: and Esau was a cunning hunter, a man of the field; and Jacob was a plain man, dwelling in tents.

As the boys grew to manhood their characters developed in sharply opposite directions. Esau became bold and courageous, delighting in the chase of the field. He returned with game for his father and enlivened the home with stirring accounts of his adventures, and this spirit and vigor won Isaac's pleasure and favor.

Jacob possessed a mild disposition that was better suited to bring happiness to his mother, and he became her favorite son. From her he had learned the divine promise given to her that the elder should serve the younger. With youthful reasoning he concluded that this promise could not be fulfilled so long as Esau retained the rights and privileges belonging to the firstborn.