Genesis 25:29

And Jacob sod pottage
Or boiled broth; this he did at a certain time, for this was not his usual employment; the Targum of Jonathan says, it was on the day in which Abraham died; and whereas this pottage was made of lentiles, as appears from ( Genesis 25:34 ) ; this the Jewish writers ^F9 say was the food of mourners; and so this circumstance furnishes out a reason for Jacob's boiling pottage of lentiles at this time: and hence also they ^F11 gather, that Jacob and Esau were now fifteen years of age; for Abraham was an hundred years old when Isaac was born, and Isaac was sixty at the birth of his sons; and Abraham lived to be one hundred and seventy five, and therefore Esau and Jacob must be fifteen years old when he died: and Esau came from the field, and be [was] faint:
for want of food, and weary with hunting, and perhaps more so, having toiled and got nothing.