The dramatic climax of the patriarchal blessings arrives in a moment of profound revelation and shock. As Isaac discovers the deception surrounding his blessing, he experiences an intense, overwhelming physical and emotional reaction. The primary approach among commentators is that this reaction is not driven by fear, but by immense astonishment and wonder [ספורנו, הכתב והקבלה, מלבי״ם, ביאור יש״ר]. Isaac is struck by the miraculous precision of the events. Jacob managed to hunt, cook, enter, and leave at the exact moment Esau arrived, with absolutely no overlap. This flawless sequence proves to Isaac that God's hand orchestrated the entire encounter. Conversely, some suggest his reaction stems from deep sorrow, realizing that his beloved son Esau has lost the blessing forever, as Jacob has been made the master with no equivalent blessing left to give [רמב״ן, הטור הארוך, תולדות יצחק]. Another perspective proposes that Isaac's outward display of shock is intentional, designed to prove to Esau that he did not collaborate in Jacob's deception [רד״ק].
On a deeper spiritual level, this moment of trembling is described as being even more severe than what Isaac experienced during his own binding on the altar. As Esau steps into the room, Isaac perceives through divine inspiration that the gates of Hell are opening beneath him. He palpably feels the dark forces of impurity and wickedness that have entered the room alongside his eldest son [רש״י, רבנו בחיי, חזקוני, גור אריה].
Caught in this storm of emotions, Isaac questions the identity of the person who had just served him. He wonders aloud who it was that had been there and where he suddenly vanished to [אבן עזרא, רד״ק, רש״י]. Through his confusion, he tries to make sense of the reality before him, reasoning that if the man standing in the room is indeed Esau, then who was the one who brought the food? [ספורנו, הכתב והקבלה]. This confusion also reflects Isaac's sheer disbelief regarding Jacob's true capabilities. He is stunned by the possibility that Jacob, whom he always considered a quiet dweller of tents, is actually a swift and capable hunter [קונטרס חיבה יתירה].
Recalling the meal he just consumed, Isaac notes that he had eaten from everything before Esau's arrival. This meal was not ordinary; he tasted every flavor in the world he could possibly desire, experiencing a brief glimpse of the World to Come [רש״י, מזרחי, תורה תמימה]. The timing of this feast is of crucial importance. Had Esau been present in the house during the blessing, the mere presence of a wicked individual would have severely tainted the spiritual atmosphere, preventing the blessings from resting upon Jacob [פרדס יוסף].
Despite the deception, Isaac does not respond with anger or curses. Instead, he firmly confirms the blessing. Realizing through divine inspiration that the blessing has already taken effect and that this outcome is ultimately God's will, Isaac makes peace with the judgment of his wife, Rebecca [רמב״ן, ספורנו, ברכת אשר]. Furthermore, to prevent any future claims that Jacob only secured his destiny through trickery, Isaac chooses in this moment to validate the blessing with his full, willing consent [רש״י, רשב״ם, חזקוני]. There is also a profound element of self-preservation in his decision. Having just declared to Jacob that those who curse him will be cursed, Isaac knows that issuing a curse now would inadvertently bring a curse upon himself, prompting him to bless Jacob instead [אור החיים, חזקוני, הדר זקנים]. By affirming the blessing, Isaac emphasizes that this is not a standard bestowal, but a supreme, eternal, and exquisite blessing that transcends the limits of time [הכתב והקבלה, כלי יקר].