Bhagavad Gita Chapter 5, Verse 24

योऽन्तःसुखोऽन्तरारामस्तथान्तर्ज्योतिरेव यः | स योगी ब्रह्मनिर्वाणं ब्रह्मभूतोऽधिगच्छति ||

yo 'ntaḥ-sukho 'ntar-ārāmas tathāntar-jyotir eva yaḥ sa yogī brahma-nirvāṇaṁ brahma-bhūto 'dhigacchati

He whose happiness is within, who delights within, and whose light is within—that yogi, having become Brahman, attains the nirvana of Brahman.

Krishna describes the yogi who attains liberation: one whose happiness is within (antaḥ-sukhaḥ), who delights within (antar-ārāmaḥ), and whose light is within (antar-jyotiḥ). That yogi (sa yogī), having become Brahman (brahma-bhūtaḥ), attains (adhigacchati) the nirvana of Brahman (brahma-nirvāṇam)—liberation. This means the yogi finds everything within—happiness, delight, and light—not in external objects. When you're established in the Self, you become one with Brahman and attain liberation. The key is turning inward—finding happiness, delight, and light within, not seeking them outside. This is the ultimate goal of karma yoga—becoming Brahman and attaining liberation.