Commentary of Charles Spurgeon, Adam Clarke & Matthew Henry
Lest there be any fornicator, or profane person, as Esau, who for 
one morsel of meat sold his birthright. For ye know how that afterward, when he would have inherited the
blessing, he was rejected: for he found no place of repentance, though
he sought it carefully with tears.
Vs.16,17
---Esau, in
his great wickedness, had made the bargain, and God in his righteous judgment,
ratified and confirmed it, and would not suffer Isaac to reverse it.---
Lest there be any fornicator - Any licentious person who would turn the Gospel of the grace of God into lasciviousness. 
Or profane person, as Esau - It is not intimated that Esau was a fornicator; and the disjunctive η,
or, separates the profane person from the fornicator. And Esau is here
termed profane, because he so far disregarded the spiritual advantages
connected with his rights of primogeniture, that he alienated the whole
for a single mess of pottage.
When he would have inherited the blessing - When
he wished to have the lordship over the whole family conveyed to him,
and sought it earnestly with tears, he found no place for a change in
his father's mind and counsel, who now perceived that it was the will of
God that Jacob should be made lord of all.
Repentance - Here μετανοια is not to be taken in a theological sense, as implying contrition for
sin, but merely change of mind or purpose; nor does the word refer here
to Esau at all, but to his father, whom Esau could not, with all his
tears and entreaties, persuade to reverse what he had done.... We may hence learn,That apostasy from Christ is the
fruit of preferring the gratification of the flesh to the blessing of God and
the heavenly inheritance.
It was done and could not be undone.
How Judas may sit side by side with favored and
true-hearted apostles, aye, and may be near the Master, too.
And, oh, friends, if
at any time the pottage should seem very sweet and we should be very
hungry, ....and we are tempted to do an unrighteous thing to get it, let
us take care, for Esau could not undo the terrible act of selling his
birthright, neither could we if we were permitted to do so.
