CHAPTER 18 · VERSE 38
Bhagavad Gita 18.38
विषयेन्द्रियसंयोगाद्यत्तदग्रेऽमृतोपमम्। परिणामे विषमिव तत्सुखं राजसं स्मृतम्॥
That happiness which arises from the contact of senses with sense objects, tasting like nectar in the beginning but turning to poison in the end, is called Rajasic.
Rajasic joy offers instant gratification (nectar first), but inevitably results in disappointment, regret, or health loss (poison later).