Bhagwad Gita
Chapter 18, Verse 35
यया स्वप्नं भयं शोकं विषादं मदमेव च।न विमुञ्चति दुर्मेधा धृतिः सा पार्थ तामसी।।18.35।।
And that determination which cannot go beyond dreaming, fearfulness, lamentation, moroseness, and illusion-such unintelligent determination is in the mode of darkness.