John Calvin Commentary Genesis 27:13

"And his mother said unto him, Upon me be thy curse, my son. Only obey my voice, and go fetch me them." — Genesis 27:13 (ASV)

Upon me be thy curse, my son. Here Rebekah sins again, because she burns with such hasty zeal that she does not consider how highly God disapproves of her evil course. She presumptuously subjects herself to the curse. But from where this unheeding confidence? Lacking any divine command, she took her own counsel.

Yet no one will deny that this zeal, although preposterous, proceeds from special reverence for the word of God. For since she was informed by the oracle of God that Jacob was preferred in the sight of God, she disregarded whatever was visible in the world, and whatever the sense of nature dictated, in comparison with God’s secret election.

Therefore, we are taught by this example that everyone should walk modestly and cautiously according to the rule of his vocation, and should not dare to proceed beyond what the Lord allows in his word.