Bhagavad Gita 18.35

यया स्वप्नं भयं शोकं विषादं मदमेव च।न विमुञ्चति दुर्मेधा धृतिः सा पार्थ तामसी ॥१८.३५॥

yayā svapnaṃ bhayaṃ śokaṃ viṣādaṃ madameva cana 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.

गीता