Genesis 27:33

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

וַיֶּחֱרַ֨ד יִצְחָ֣ק חֲרָדָה֮ גְּדֹלָ֣ה עַד־מְאֹד֒ וַיֹּ֡אמֶר מִֽי־אֵפ֡וֹא ה֣וּא הַצָּֽד־צַ֩יִד֩ וַיָּ֨בֵא לִ֜י וָאֹכַ֥ל מִכֹּ֛ל בְּטֶ֥רֶם תָּב֖וֹא וָאֲבָרְכֵ֑הוּ גַּם־בָּר֖וּךְ יִהְיֶֽה׃

And Yiżĥaq trembled very much, and said, Who then is he that has taken venison, and brought it me, and I have eaten of all before thou camest, and have blessed him? moreover, he shall be blessed.