Rashi on Genesis 27:33/רש"י על בראשית כ״ז:ל״ג

1ויחרד [AND ISAAC] TREMBLED — Explain it as the Targum renders it ותוה, which means he was perplexed. The Midrashic explanation (Midrash Tanchuma, Toldot 11) is that he saw Gehinnom opening beneath him (Esau).

2מי אפוא WHO THEN IS HE — The word אפוא is an independent particle having no etymological connection with any other Hebrew word and is used with many different shades of meaning Another explanation of אפוא is that it is the same as איה פה where here, — so that מי אפוא means “Who is he and where is he here that hath hunted venison”?)

3ואכל מכל AND I HAVE EATEN OF ALL — all tastes that I desired to find in it I indeed found therein (Genesis Rabbah 67:2).

4גם ברוך יהיה YEA, AND HE SHALL BE BLESSED — In order that you may not say “If Jacob had not deceived his father he would never have received the blessing”, he, therefore, confirmed it, blessing him now of his own free will (Genesis Rabbah 67:2).