With their minds fixed on That, their selves absorbed in That, devoted to That, and holding That as their highest goal, they go to a state from which there is no return, their impurities washed away by knowledge.
Explanation
Krishna continues from the previous verse, where knowledge of the Self shines like the sun. "That" (tat) refers to the supreme reality, Brahman or the Self, known through that knowledge. Those whose understanding (buddhi), identity, steady commitment and aim all rest in it are cleansed of impurity (kalmaṣa) and reach liberation, with no return to rebirth (apunarāvṛtti). Traditions differ on whether "That" is the formless Self, as non-dualist readings take it, or the Lord himself, as devotional readings take it.