Bhagavad Gita Verse 18.25

जो कर्म परिणाम, हानि, हिंसा और सामर्थ्य को न विचार कर केवल अज्ञान से आरम्भ किया जाता है, वह तामस कहा जाता है ।

The work which one completes with a confused mind and deluded intelligence, without any cares about the horrible consequences that might result from his selfish tasks; work that is done without concern for the bondage that it creates for the performer; work done without any heed to injury or harm that might come to others because of one’s (evil) actions; or work accomplished without worrying about one’s own loss; these are work done out of darkness by those who are known as Tamsic-natured people.