Chapter 18 · verse 22 · gita.yoga.org

Bhagavad Gita 18.22

यत्तु कृत्स्नवदेकस्मिन्कार्ये सक्तमहैतुकम्।अतत्त्वार्थवदल्पं च तत्तामसमुदाहृतम्

But that which clings to one single effect as if it were the whole, without reason, without any foundation in Truth, and is trivial—that is declared to be Tamasic.