John Calvin Commentary Genesis 27:5

"And Rebekah heard when Isaac spake to Esau his son. And Esau went to the field to hunt for venison, and to bring it." — Genesis 27:5 (ASV)

And Rebekah heard. Moses now explains more fully the scheme by which Jacob obtained the blessing. It truly appears ridiculous that an old man, deceived by the cunning of his wife, should, through ignorance and error, have spoken what was contrary to his wish. And surely Rebekah's scheme was not without fault; for although she could not guide her husband with wise advice, it was not a legitimate way of acting to circumvent him with such deceit.

For, as a lie is in itself blameworthy, she sinned more seriously still in this: that she desired to treat a sacred matter lightly with such deceptions. She knew that the decree by which Jacob had been elected and adopted was unchangeable; why then does she not patiently wait until God confirms it in fact, and shows that what He had once pronounced from heaven is certain?

Therefore, she obscures the heavenly oracle by her lie, and abolishes, as much as she could, the grace promised to her son. Now, if we consider further from where this great desire to act arose, her extraordinary faith will on the other hand appear. For, as she did not hesitate to provoke her husband against herself, to ignite irreconcilable hostility between the brothers, to expose her beloved son Jacob to the danger of immediate death, and to disturb the whole family, this certainly flowed from no other source than her faith. The inheritance promised by God was firmly fixed in her mind; she knew that it was decreed for her son Jacob.

And therefore, relying on the covenant of God and keeping in mind the oracle received, she forgets the world. Thus, we see that her faith was mixed with an unjust and excessive zeal. This is to be carefully observed, so that we may understand that a pure and distinct knowledge does not always so illuminate the minds of the pious as to cause them to be governed, in all their actions, by the Holy Spirit, but that the little light which shows them their path is enveloped in various clouds of ignorance and error; so that while they hold a right course and are tending towards the goal, they yet occasionally slide.

Finally, both in Isaac and in his wife the principle of faith was preeminent. But each, by ignorance in certain particulars and by other faults, either diverged a little from the way or, at least, stumbled in the way. But seeing that, nevertheless, the election of God stood firm; indeed, He even executed His design through the deceit of a woman, He vindicates, in this manner, the whole praise of His blessing to His own unmerited goodness.