yo ’ntah-sukho ’ntar-aramas
tathantar-jyotir eva yah
sa yogi brahma-nirvanam
Word for word:
yah — one who; antah-sukhah — happy from within; antah-aramah — actively enjoying within; tatha — as well as; antah-jyotih — aiming within; eva — certainly; yah — anyone; sah — he; yogi — a mystic; brahma-nirvanam — liberation in the Supreme; brahma-bhutah — being self-realized; adhigacchati — attains.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
One whose happiness is within, who is active and rejoices within, and whose aim is inward is actually the perfect mystic. He is liberated in the Supreme, and ultimately he attains the Supreme.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Unless one is able to relish happiness from within, how can one retire from the external engagements meant for deriving superﬁcial happiness? A liberated person enjoys happiness by factual experience. He can, therefore, sit silently at any place and enjoy the activities of life from within. Such a liberated person no longer desires external material happiness. This state is called brahma-bhuta, attaining which one is assured of going back to Godhead, back to home.