Chapter 18 · Liberation through Renunciation · Krishna said
Bhagavad Gita 18.25 — Tamasic action
अनुबन्धं क्षयं हिंसामनपेक्ष्य च पौरुषम्। मोहादारभ्यते कर्म यत्तत्तामसमुच्यते ॥
anubandhaṃ kṣayaṃ hiṃsāmanapekṣya ca pauruṣam | mohādārabhyate karma yattattāmasamucyate ||
Meaning
Action started out of confusion, without thinking of its result, the loss, the harm to others or one's own ability, is called tamasic.