The Shaikh of Islaam Ibn Taymiyyah, may Allaah have mercy on him, said, “Purifying the soul, acting upon knowledge, and fearing Allaah have a tremendous effect on obtaining knowledge.” Mowqif Ibn Taymiyyah minas-Soofiyyah, vol. 1, p. 357.
Al-Fudayl ibn 'Iyyad said, "If you are asked whether you fear Allah, do not reply; for of you say 'Yes' you would be lying, and if you say 'No' it would mean that you do not believe in Him."