Bhagavad Gita · 5.24

योऽन्तःसुखोऽन्तरारामस्तथान्तर्ज्योतिरेव यः।स योगी ब्रह्मनिर्वाणं ब्रह्मभूतोऽधिगच्छति॥

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

One who finds happiness within, who rejoices within, and who is illumined within — that yogi, having become Brahman, attains liberation in Brahman.

— Bhagavad Gita 5.24

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)