Chapter 18 · Liberation through Renunciation · Krishna said
Bhagavad Gita 18.39 — Tamasic happiness
यदग्रे चानुबन्धे च सुखं मोहनमात्मनः। निद्रालस्यप्रमादोत्थं तत्तामसमुदाहृतम् ॥
yadagre cānubandhe ca sukhaṃ mohanamātmanaḥ | nidrālasyapramādotthaṃ tattāmasamudāhṛtam ||
Meaning
Happiness that clouds the mind from beginning to end, born of sleep, laziness and carelessness, is tamasic.