1 Gita Sloka Every Day - Chapter 18 - Moksha Sanyasa Yoga - Sloka 25

The entire content of this mail is from Shri V N Gopala Desikan's  Srimad Bhagavad Gita, published by Vishishtadvaita Research Centre, Chennai and The Bhagavad Gita by Swami Chidbhavananda published by Ramakrishna Mission

The Three Gunas Give Impetus to Karma - 18-40

1 Gita Sloka  Every Day - Chapter 18 - Moksha Sanyasa Yoga - Sloka 25

Ramanujar at Kanchi

Anubandham kshayam himsam anapekshya cha paurusham I

Moha arabhyate karma yat tat tamasam uchyate II sloka 25

अनुबन्धं क्षयं हिंसां अनपेक्ष्य च पौरुषं I 
मोहा आरभ्यते कर्म यत्  तत् तामसं उच्यते II श्लोक 25

That action which is undertaken from delusion, without heed to the consequence, loss, injury and ability is declared to be Tamasaika.

The Bhagavad Gita by Swami Chidbhavananda published by Ramakrishna Mission

The man immersed in tamasika is not able to discern whether he is undertaking good or bad, much less the consequence of it. Loss of energy, property and money, time - these reverses do not occur to him as bad. His endeavours are harmfulboth to him and oters. It is not within his ken that his resources fall too short of the project which he has launched. The doings of such a man are born of tamas

Shri V N Gopala Desikan's  Srimad Bhagavad Gita, published by Vishishtadvaita Research Centre

That karma which is started by delusion, thinking that he is the doer; not knowing that the Lord actually gets the things done through him; without considering (a) the pain which follows the work done (b) LOss of wealth in doing the work (c) Injury caused to other living beings; and with out knowing his own capacity to do the work; such a work is called as tamasika