Allah T'ala says in the Holy Quran, Surah 35 (Al-Fatir):

35:27 Seest thou not that Allah sends down rain from the sky? With it We then bring out produce of various colours. And in the mountains are tracts white and red, of various shades of colour, and black intense in hue.

35:28 And so amongst men and crawling creatures and cattle, are they of various colours. Those truly fear Allah, among His Servants, who have knowledge: for Allah is Exalted in Might, Oft-Forgiving.

The more a person is unaware of the attributes of Allah, the more he will be fearless of Him. Contrary to this, the more a person is aware and conscious of Allah's powers, His knowledge, His wisdom, His vengeance and His omnipotence and His other attributes, the more he will fear His disobedience. Thus, in fact, "knowledge" in this verse does not imply knowledge of academic subjects like philosophy and science and history and mathematics, etc. but the knowledge of Divine attributes, no matter whether one is literate or illiterate. The one who is fearless of God is illiterate merely as regards this knowledge even if he has All the knowledge of the world. And the one who knows the attributes of God and fears Him in his heart, is Iearned even if he is illiterate. In the same connection, one should also know that in this verse the ' ulama ' does not imply the scholars in the technical sense, who are termed as religious scholars because of their knowledge of the Qur'an and Hadith and Fiqh and philosophy. They will prove true to this verse only when they possess fear of God in their hearts. The same thing has been said by Hadrat 'Abdullah bin Mas'ud, thus: "knowledge is not due to much narration of Hadith but due to much fear of Allah." And also by Hadrat Hassan Basri, thus: "The scholar is he who fears Allah though he has not seen Him, and turns to what is approved by Him and keeps away from what makes Him angry." (Tafheemul Quran)