Chapter 5, Verse 21
Part of 5: Karm Sanyās Yog — कर्मसंन्यासयोगबाह्यस्पर्शेष्वसक्तात्मा विन्दत्यात्मनि यत्सुखम्। स ब्रह्मयोगयुक्तात्मा सुखमक्षयमश्नुते॥
bāhya-sparśheṣhvasaktātmā vindatyātmani yat sukham sa brahma-yoga-yuktātmā sukham akṣhayam aśhnute
With the self unattached to external contacts, he finds happiness in the Self; with the self engaged in the meditation of Brahman, he attains endless happiness.
When the mind is not attached to external objects of the senses, when one is deeply engaged in the contemplation of Brahman, he finds undecaying bliss in the Self within. If you want to enjoy the imperishable happiness of the Self within, you will have to withdraw the senses from their respective objects and plunge yourself in deep meditation on the Self within. This is the gist of this verse.