अनुबन्धं क्षयं हिंसामनवेक्ष्य च पौरुषम् ।
मोहादारभ्यते कर्म यत्तत्तामसमुच्यते ॥ १८.२५ ॥

anubandham kṣayam himsām-anavekṣya ca pauruṣam |
mohād-ārabhyate karma yat-tat-tāmasam-ucyate || 18.25 ||

Action – the tāmasika kind

That action, which causes bondage and decay, involving violence, conceived without considering one’s capacity, and initiated by delusion, is said to be tāmasika in nature.

Tāmasika activity does not care about the consequences it will bring about. There is no thought whether it will cause damage or loss to oneself or injury to others around. It also does not consider whether the actor has sufficient capacity for the purpose. Everywhere delusion is at work. No proper understanding is aimed at. It is more a visible activity, than a well-considered and purposeful one.