3:39  

आवृतं ज्ञानमेतेन ज्ञानिनो नित्यवैरिणा ।
कामरूपेण कौन्तेय दुष्पूरेणानलेन च ॥३- ३९॥

aawRRitaM dnyaanametena dnyaanino nityawairiNaa ।

kaamaroopeNa kaunteya duShpooreNaanalena cha ॥३- ३९॥

Source: Automatic ITRANS Transliteration

Covered is the knowledge of the knowledgeable by this eternal foe,
In the form of lust, O son of Kunti, insatiable fire as well.

Also, the knowledge of the knowledgeable is obscured by this eternal foe, O son of Kunti, insatiable fire in the form of lust.

Source: Milind S. Pandit

O Arjuna, Jnana gets covered by this insatiable fire of Kaama, the eternal enemy of Jnani.

Source: The Bhagavad-Gita: The Sacred Song

Thus, a man's pure consciousness is covered by his eternal enemy in the form of lust, which is never satisfied and which burns like fire.

Source: Bhagavad Gita As It Is