Genesis 25:26, 33-34

Then the other twin was born with his hand grasping Esau’s heel. So they named him Jacob. Isaac was sixty years old when the twins were born.

But Jacob said, “First you must swear that your birthright is mine.” So Esau swore an oath, thereby selling all his rights as the firstborn to his brother, Jacob. Then Jacob gave Esau some bread and lentil stew. Esau ate the meal, then got up and left. He showed contempt for his rights as the firstborn.