योऽन्तःसुखोऽन्तरारामस्तथान्तर्ज्योतिरेव यः। स योगी ब्रह्मनिर्वाणं ब्रह्मभूतोऽधिगच्छति ॥

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

He who is happy within, who rejoiceth within, who is illuminated within, that Yogî, becoming the Eternal, goeth to the Peace of the Eternal.

In plain words: Krishna says that the yogi, a person who practices joining with God, whose happiness, joy and light come from within, becomes one with God and reaches God's peace.