Verse
अधर्मं धर्ममिति या मन्यते तमसावृता ।सर्वार्थान्विपरीतांश्च बुद्धिः सा पार्थ तामसी ॥
That which, enveloped in darkness, takes what is not the true law and upholds it as the law and sees all things in a cloud of misconceptions, that understanding , O Partha, is tamasic.
Gītā 18·32