Bhagavad Gita Chapter 5, Verse 22

ये हि संस्पर्शजा भोगा दुःखयोनय एव ते | आद्यन्तवन्तः कौन्तेय न तेषु रमते बुधः ||

ye hi saṁsparśa-jā bhogā duḥkha-yonaya eva te ādyantavantaḥ kaunteya na teṣu ramate budhaḥ

The pleasures born of contact with sense objects are indeed sources of pain, having beginning and end. The wise person does not delight in them.

Krishna explains why the wise don't seek external pleasures: the pleasures (bhogāḥ) born of contact with sense objects (saṁsparśa-jā) are indeed sources of pain (duḥkha-yonaya eva). They have beginning and end (ādyantavantaḥ)—they're temporary. The wise person (budhaḥ) does not delight (na ramate) in them (teṣu). This means external pleasures are temporary and ultimately lead to pain—they create attachment, which leads to suffering. The wise understand this, so they don't seek external pleasures. They find happiness in the Self instead, which is permanent and doesn't lead to pain. This understanding supports the yogi's detachment from external objects.