What do we learn from "ha'Chacham Einav b'Rosho"?
Rashi: At the beginning of a matter, he sees what will be in the end. Seforno - therefore, sometimes he despises a pleasure, to flee from future damage. This requires non-physical intellect, to judge the future.
Ibn Ezra: A Chacham is compared to a seeing man with eyes in his head. He goes wherever he wants, and sees the straight and crooked paths.
Rashbam: He guards himself to go in light.
Ri Kara: His Chachmah illuminates for him, and teaches him what to do, like one who walks in daylight, and using his eyes he goes in a straight path and does not stumble.
Rid: This is how the advantage of Chachmah over folly is seen.
Metzudas David: A Chacham know that his eyes are in his head, in a high place, in order that he will see afar. Therefore, he looks far in advance to contemplate his ways, and not stumble in them.
What do we learn from "veha'Kesil ba'Choshech Holech"?
Eruvin 6b: Before the Bas Kol (voice from Heaven) announced that the Halachah follows Beis Hillel, one could choose to follow either school. If one follows the leniencies of both, he is wicked. It says about one who follows the stringencies of both "veha'Kesil ba'Choshech Holech" [if the stringencies are inconsistent; if they do not contradict each other, one may follow both]. Rather, one should consistently follow Beis Shamai, or consistently follow Beis Hillel.
Ibn Ezra: He does not know on what he will stumble. Rashbam - he falls.
Ri Kara: He is like one who goes in darkness and does not know, and stumbles very soon.
Seforno: He does not see the future, and he is trapped.
Metzudas David: A Kesil does not look far in advance. It is as if he walks in darkness, where one cannot see, and he bangs his foot on stumbling blocks. If not for the Kesil, the good of the Chacham, who does not stumble, would not be known. If not for darkness that inhibits one from guarding from stumbling, the sweetness of light, which saves from stumbling, would not be known.
Why does it say "v'Yadati Gam Ani"?
Rashi: Also I, who praise the Chacham over the Kesil, I know that both of them will die.
Ri Kara: Do not say that since Chachmah is so praised, it is not Hevel. Since the Chacham will die like the fool, also Chachmah is Hevel.
Metzudas David: Even though the Chacham will die just like the Kesil, one should despise Sichlus.
