Bhagavad Gita 18.32

अधर्मं धर्ममिति या मन्यते तमसावृता |
सर्वार्थान्विपरीतान्श्च बुद्धिः सा पार्थ तामसी

Translation

That intellect which is shrouded in darkness, imagining irreligion to be religion, and perceiving untruth to be the truth, is of the nature of ignorance, O Parth.