Bhagavad Gita 18.35

यया स्वप्नं भयं शोकं विषादं मदमेव च।न विमुञ्चति दुर्मेधा धृतिः सा पार्थ तामसी॥

yayā svapnaṃ bhayaṃ śokaṃ viṣādaṃ madameva ca |na vimuñcati durmedhā dhṛtiḥ sā pārtha tāmasī ||

That firmness, O Arjuna, by which a stupid man does not abandon sleep, fear, grief, despair, and conceit, is Tamasic.

And that which clings perversely to false idealism, fear, grief, despair, and vanity is the product of ignorance.

Our plain-language meaning of this verse is waiting for scholar review.