Whose self is unattached to external contacts, he finds happiness in the self (ātman). He, whose self is disciplined in the yoga of Brahman, enjoys imperishable happiness.
Detached from external contacts, he discovers joy in himself; joined by discipline to the infinite spirit, the self attains inexhaustible joy.
(21) [His] self detached from contacts with the outside world, in [him]self so finds his joy, [his] self in Brahman integrated by spiritual exercise (brahma-yoga-yukt’ātmā), he finds unfailing joy.
5.21 With his heart unattached to external objects, he gets the bliss that is in the Self. With his heart absorbed in meditation on Brahman, he acquires undecaying Bliss.
5.21 He whose mind is detached from external contact, and finds happiness in the self --- he has his mind engaged in the contemplation of Brahman and he enjoys undecaying bliss.
5.21 With the self unattached to external contacts he finds happiness in the Self; with the self engaged in the meditation of Brahman he attains to the endless happiness.