Keeping the self steadily engaged in this way, the yogi, free from impurity, easily experiences the contact with Brahman, a happiness without end.
Explanation
Krishna is continuing his teaching to Arjuna on meditation, building on the previous verse. A yogi (one practicing disciplined union of the self with the highest reality) who keeps the mind constantly engaged becomes free of impurity (kalmaṣa) and comes into contact with Brahman, the ultimate reality. Non-dual readings take Brahman here as the self's own identity with the absolute, while devotional traditions take it as closeness to God; both agree it is lasting joy.