Fear of God is called “the first mitzva” and is the gateway to belief and to keeping the rest of the mitzvot. There are a number of types of fear, including fear of the Holy One, blessed be He, that stems from fear of physical punishment or of spiritual punishment in the World to Come, that are not so praiseworthy. The main type of fear is the higher fear, awe of the Holy One, blessed be He, Himself, and His greatness.

Fear is the first mitzva:

Rabbi Shimon began speaking about the Torah’s mitzvot, and said: All of the mitzvot that the Holy One, blessed be He, gave Israel are written in the Torah as a principle: “In the beginning, God created [the heavens and the earth]” (Genesis 1:1). This is the first of all mitzvot, and is referred to as fear of God, which is called “beginning”… This is the gateway through which one enters [the realm of] belief, and the world exists based on this mitzva…

The main fear is fear of God, not of sin:

Fear is divided into three types, two of them secondary and one of them primary. A person can be afraid of the Holy One, blessed be He, in order that his children will live [if he obeys God] and not die. He might also be afraid of physical or monetary punishment, and this might cause constant fear. People with those fears have not made the Holy One, blessed be He, their main focus. A man might be afraid of the Holy One, blessed be He, because he is afraid of punishment in this world or in Gehenna. These two are not the primary and fundamental types of fear. The primary type of fear is being in awe of one’s Master, who is great and who controls, is the foundation and root of all of the worlds, and everything is as naught before Him. (Zohar 1:11b)

There are internal and external types of fear. Internal fear is even higher than love of God. External fear is fear of rebelling against the Holy One, blessed be He, and getting punished. Internal fear, on the other hand, is what a person feels when he meditates on how great God is and how small man is in comparison. He feels unworthy of standing in His presence.

You should be aware of the statement of the kabbalists, that there are two types of fear, internal and external fear. External fear is lower than love of God and internal fear is higher than love. How is this possible? External fear is being afraid of transgressing the King’s commandment lest he be punished and held accountable to the King’s word. Internal fear is understanding the greatness of the Creator, may He be elevated, and the great spiritual delight, wealth, and honor in His palace. When a person appreciates this, he will be afraid and alarmed and say, “Maybe I am not worthy of standing in the King’s palace. For considering my great potential and lowly state and shortcomings, perhaps He will find fault with me… This is the fear that is above love. (Rabbi Menaĥem Recanati, Vayera)

Further reading: For more on reward and punishment, see p. 256; A Concise Guide to the Sages, p. 165.