Shaykh Muhammad ibn Saalih al Uthaymeen, rahimahullaah, said:
“The foundation of knowledge is khashyah (fear and awe) of Allaah, the Most High”. And this statement of Imaam Ahmad is correct: the foundation of knowledge is khashyah of Allaah.
And khashyah of Allaah is fear of Allaah which is built upon knowledge and glorification (of Him). And for this reason, Allaah the Most High, said:
It is only the people of knowledge from amongst His servants who have khashyah of Allaah. [Soorah Faatir (35) aayah 28]
So if a person has true knowledge of Allaah, the Mighty and Majestic, and if he has true awareness and knowledge of Him, then khashyah of Allaah will inevitably be established in his heart. (This is) because if he has knowledge of that, having knowledge of a Lord who is ‘Adheem (Tremendous), of a Lord who is Qawee (Perfect in strength), of a Lord who is Qaahir (Invincible Subduer), of a Lord who is All Knowing of that which the person keeps secret and hidden, then you will find him (that person) establishing obedience to Allaah, the Mighty and Majestic in a complete manner.
It is only the people of knowledge from amongst His servants who have khashyah of Allaah. The scholars have said: The distinction between khashyah (fear and awe) and khawf (fear) is that khashyah occurs due to tremendous greatness of the one being feared – and khawf occurs due to the weakness of the one who has the fear, even if the one being feared (with khawf) is not tremendous and great… So in summary, khashyah is more tremendous than khawf – but sometimes it is said, ‘have khawf of Allaah’. He, the Most High, said:
So do not have khawf of them, but rather have khawf of Me if you truly believe. [Soorah aale ‘Imraan (3) aayah 175]
And this is (being said) in direct opposition to the action of those who have khawf of the people.
(Sharh hilyah taalib il ‘ilm p23 of Shaykh Muhammad ibn Saalih al ‘Uthaymeen rahimahullaah, translator Nasser ibn Najam, checked by Abu Talhah Dawood Burbank)