R. Yonah: It is one Midah, and it is the source of all honored actions. There are honored Midos, and each has many derivatives, and awesome deeds depend on them. Yir'as Hashem is the source of all Midos. It is the base of all honored Midos and actions - "ba'Shem Yitzdeku v'Yis'halelu Kol Zera Yisrael" (Yeshayah 45:25). There is no one who does not sin, a little or a lot. The absolute proof of the level of fear of created beings is fear of the king.

Malbim: The way of Chachmah is the way of life. There are pitfalls of death around it - the fortress of the Yetzer and desire, which want make the Nefesh fall to the path of death. Even though he knows the laws of Chachmah, he is not secure, lest the ambush that sits inside not trap it with its nets. However, via Yir'ah, he afflicts the powers of the Nefesh. There is the source of life. One who drinks its waters will live eternal life and veer from lethal pitfalls. Fear without Torah and Chachmah does not help, for he does not know what to do and what is the way of Chachmah - if there is no Chachmah there is no fear.