Bhagavad Gita · 3.38

धूमेनाव्रियते वह्निर्यथादर्शो मलेन च।यथोल्बेनावृतो गर्भस्तथा तेनेदमावृतम्॥

dhūmenāvriyate vahnir yathādarśho malena cha yatholbenāvṛto garbhas tathā tenedam āvṛtam

As fire is covered by smoke, as a mirror by dust, and as an embryo by the womb, so is knowledge covered by desire.

— Bhagavad Gita 3.38

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)