Knowledge is one of the main causes of God-fearing

Allah Almighty said: “Among His slaves, only those who have knowledge fear Allah” (Fatir, 35:28).

 Sheikh ‘Abdur-Rahman al-Si’di (may Allah have mercy on him) said in the interpretation of this verse : “The Lord said that only those slaves who have knowledge are afraid of Him. The better a person gets to know Him, the more he fears His punishment. This fear makes a person avoid sins and prepare to meet Him.”
See “Tafsirul-Karimi-Rrahman”.

Imam Ibn Qayyim al-Jawziya, may Allah have mercy on him, in the interpretation of this verse said: “Only the one who fears Allah is the one who knows, and therefore only the one who knows is afraid of Him. And whoever is knowledgeable, except as professing God-fearing. And therefore, if there is no knowledge, there is no fear, and if there is no fear, then this indicates a lack of knowledge.
See Tafsir ibn Qaim.

 Ibn Jarir at-Tabari, in the interpretation of this verse, said: “The Almighty meant that only those who fear Allah and fear His punishment through charitable deeds are those who know that Allah is capable of every thing, that He does whatever He wants, because the one who knows this is convinced that Allah punishes disobedience, and this makes him fear Allah.
See Tafsir al-Tabari (13/132).