Bhagavad Gita: Chapter 18, Verse 39

यदग्रे चानुबन्धे च सुखं मोहनमात्मन: |
निद्रालस्यप्रमादोत्थं तत्तामसमुदाहृतम् || 39||

yad agre chānubandhe cha sukhaṁ mohanam ātmanaḥ
nidrālasya-pramādotthaṁ tat tāmasam udāhṛitam

yat—which; agre—from beginning; cha—and; anubandhe—to end; cha—and; sukham—happiness; mohanam—illusory; ātmanaḥ—of the self; nidrā—sleep; ālasya—indolence; pramāda—negligence; uttham—derived from; tat—that; tāmasam—in the mode of ignorance; udāhṛitam—is said to be

yad agre chanubandhe cha sukham mohanam atmanah
nidralasya-pramadottham tat tamasam udahritam

Translation

BG 18.39: That happiness which covers the nature of the self from beginning to end, and which is derived from sleep, indolence, and negligence, is said to be in the mode of ignorance.

Commentary

Tāmasic happiness is of the lowest kind and is foolishness from beginning to end. It throws the soul into the darkness of ignorance. And yet, since there is a tiny experience of pleasure in it, people get addicted to it. That is why cigarette smokers find it difficult to break their habit, even while knowing fully well it is harming them. They are unable to reject the happiness they get from the addiction. Shree Krishna states that such pleasures—derived from sleep, laziness, and negligence—are in the mode of ignorance.