מדרש אויף משלי 17:15

“One who exonerates the wicked and one who condemns the righteous, both of them are an abomination to the Lord” (Proverbs 17:15) – Rabbi Yehoshua ben Levi said: It was not because Rebecca loved Jacob more than Esau that she performed this action, but she said: ‘Let him [Esau] not enter and mislead that elder [Isaac],’ based on: “Both of them are an abomination to the Lord.” Because he exonerated the wicked, his eyes dimmed – “it was when Isaac was old, and his eyes dimmed.”