Bhagavad Gita 18.25

अनुबन्धं क्षयं हिंसामनपेक्ष्य च पौरुषम्। मोहादारभ्यते कर्म यत्तत्तामसमुच्यते

anubandhaṁ kṣhayaṁ hinsām anapekṣhya cha pauruṣham mohād ārabhyate karma yat tat tāmasam uchyate

That action which is undertaken from delusion, without regard for the consequences, loss, injury, and one's own ability, is declared to be Tamasic (dark).

जो कर्म परिणाम, हानि, हिंसा और सामर्थ्यको न देखकर मोहपूर्वक आरम्भ किया जाता है, वह तामस कहा जाता है।