ויאמר יעקב מכרה כיום את בכורתך לי, “And Yaakov said, ‘sell me your birthright today’” (25:31). The word כיום, today, seems extra. Why couldn’t a simple “sell me your birthright” suffice?
The answer is Yaakov negotiated the purchase of the birthright on the day of their grandfather Avraham’s passing. The whole world mourned over this loss. Statesmen and dignitaries cried out in public, “Woe to the world that has lost its leader, woe to the ship that has lost its captain!” (Bava Batra 91b). Many different types of people came to pay their last respects to Avraham, one of the greatest people in the world. The only one who was not present at his funeral was his own grandson Esav.
After the funeral, Yaakov returned home to prepare a meal for the mourners. Esav returned to the house as his brother was preparing the meal. Esav had come from the field where he was hunting, and he came in crying over the great loss of his grandfather. Yaakov was upset and ashamed at his brother for being so inconsiderate as not to show up at his own grandfather’s funeral, so he said to Esav at that moment to sell his birthright because of what happened “today.” The firstborn, Yaakov knew, was to work in the Bait Hamikdash, but an insensitive and callous firstborn like Esav was not worthy of working in such a holy place.