Rashi on Genesis 25:28/רש"י על בראשית כ״ה:כ״ח

1בפיו [THERE WAS HUNTING] IN HIS MOUTH — Understand this as the Targum renders it: in Isaac’s mouth (i. e. Isaac ate the venison he brought home). But its Midrashic explanation is: there was hunting in Esau’s mouth, meaning that he used to entrap and deceive him by his words (Genesis Rabbah 63:10).