Apparently, Isaac either didn’t believe Rebekah had a vision (Genesis 25:22-23), or he didn’t believe Rebekah’s interpretation of it. Moreover, it also seems that, if he knew of Esau’s selling his birthright to Jacob (Genesis 25:29-34), he had to have dismissed it, believing that only he had the power to transfer the Lord’s blessing to his descendants, and in that power of transference, he also had the power to choose, whom he would bless. Nevertheless, if this argument is correct as presented, Isaac was wrong on all counts but one.
While he did, indeed, have the authority to transfer Abraham’s blessing to his own descendant, a firstborn son could, indeed, lose his birthright, just as it occurred that Isaac and not Ishmael received the blessing from Abraham. Moreover, Rebekah did have a vision, and she interpreted it correctly. In other words, Isaac had the authority to transfer the blessing to one of his sons, but he did not, necessarily, have the authority to choose, which of his sons would inherit. After all, if Abraham had that authority, the blessings would have come through Ishmael! Therefore, it is the Lord who determines whom he will bless (cp. Romans 9:16).
Almost immediately after Jacob left Isaac’s tent, his brother, Esau, came in after his hunt. Announcing his presence, he brought in the meat he had cooked, asking his father to arise and eat, and then bless him, as he had promised to do (Genesis 27:30-31; cp. 27:3-4). Isaac arose and asked, who this might be, and Esau identified himself as his son (Genesis 27:32). Therefore, Isaac trembled upon hearing the voice of Esau (Genesis 27:33), who was now present with him with the meal Isaac had asked for!
Isaac must have known about the vision that Rebekah had prior to the birth of their sons (Genesis 25:22-23). Moreover, they must have discussed it, some may even have been heated discussions, wherein Isaac refused to believe Rebekah or refused to believe what she thought the vision meant. Now, however, the thing became clear. He should have believed his wife, and throughout the lives of his sons, he preferred the one the Lord had rejected.
Looking back, one could understand Abraham’s own desire to have Ishmael blessed. While Isaac was yet unborn, Abraham loved his son, Ishmael, but he was helpless to make him the one the Lord would bless. After Isaac was born, Sarah, Abraham’s wife also rejected Ishmael as an heir, and the Lord supported her desire. Although Isaac worked to bless the son he preferred, he now understood that his wife, Rebekah, was correct all along. The Lord would not have permitted such a thing to occur, unless it was his will from the beginning. Isaac chose to do only those things that Abraham did, but he failed to understand the gravity of Abraham’s decision to bless him rather than Ishmael. The right of the firstborn is founded upon human tradition, but the Lord isn’t obligated to respect human tradition. If his will is against it, the will of God trumps the tradition of men.
Indeed, Isaac was astonished, when he realized what had occurred (Genesis 27:33). While he worked toward one end, the Lord caused his blessing to go to another! The Lord would later tell Moses: “I will have mercy on whom I will have mercy, and I will have compassion on whom I will have compassion” (Exodus 33:19; cp. Romans 9:15). Therefore, it became apparent before Isaac’s own dim eyes that ‘it is not of him that wills (Isaac; Genesis 27:1-4), neither is it of him that runs (Esau; Genesis 27:30-31), but, rather, it is of God, who shows mercy upon whomsoever he wishes (Romans 9:16; Exodus 33:19).
When Esau understood what had just occurred, he cried, pleading with Isaac, his father to bless him (Genesis 27:34), but it was too late (Hebrews 12:17). He had shown little respect or value for the blessing the Lord could have given him (Genesis 25:29-34). Isaac may have considered the matter of Esau’s selling his birthright as something trivial or something Jacob and Esau had no right to do in the first place, because the authority to transfer the blessing was his to make. Nevertheless, the Lord took Esau’s decision seriously, and considered the matter settled (cp. Hebrews 12:16). The end was foreseen from the beginning (Genesis 25:22-23), and Isaac admitted that he was powerless to undo what he had done in blessing Jacob instead of Esau (Genesis 27:35).
However, Esau wasn’t so spiritually inclined, and his anger burned against his brother, Jacob (Genesis 27:36), but he asked if Isaac could bless him with another blessing. However, Isaac had not only blessed Jacob with the wealth and the blessing of Abraham, but he had made Esau, Jacob’s servant (Genesis 27:37), and how could that be undone now?
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