In The Name of Allaah, The Most Merciful, The Bestower of Mercy

Allaah [The Most High] said:

إِنَّمَا يَخْشَى اللَّهَ مِنْ عِبَادِهِ الْعُلَمَاءُ ۗ

It is only those who have knowledge among His slaves that fear Allah.
[Surah Faatir’ Aayah 28]

They are [truly] acquainted with the Greatness of Allaah and His Perfection [i.e. the Perfection of Allaah’s Lordship, Names and Attributes, Actions, Judgements, Commands, Prohibitions etc], His Rights and the rights of His slaves [i.e. the rights of mankind, Jinn and all other creatures]. They [truly] distinguish between halaal and haraam, between what is harmful and what is beneficial [i.e. what will benefit the people in their religious and worldly affairs & what will harm them]; so they have a much greater piety, fear of Allaah founded upon knowledge of Allaah’s Greatness, Perfect Sovereignty and Dominion, and being constantly aware of the fact that Allaah knows, hears and sees everything they conceal and proclaim.

As for the Jaahil, he is not [or not truly] acquainted with the Greatness of Allaah nor the rights of Allaah. How can he fear [or truly] fear Allaah when he is not [or not truly] acquianted with Allaah’s punishment and what is within the fire of hell, the Barsakh [i.e. the life after death and before the day of judgement], life in the grave and the severe anxiety people will encounter [i.e. due to one’s evil deeds].

Marhaban Yaa Taalibal Ilm’ page 240. slightly paraphrased