B.G 5.21

bāhyasparśeṣvasaktātmā vindatyātmani yat sukham। sa brahmayogayuktātmā sukhamakṣayamaśnute ॥21॥

The one who is disinterested in the external engagement of sense organs, experiences within himself happiness. The person engaging in the practice of 'Brahma-Yoga' obtains the same happiness in everlasting proportion.

Gīta Bhāshya 5.21

The remaining part of this chapter explains the combined knowledge of renunciation and Yoga. Superiority of Yōga over mere renunciation is clarified by emphasizing the undiminishing happiness one gets through Brahma-Yōga .

sanyāsa yoga jñānāni militvā prapañcayati adhyāya śeṣeṇa।

The remaining part of this chapter explains the combined knowledge of renunciation and Yoga.

punaḥ yogasya ādhikyaṁ spaṣṭayati - bāhyasparśeṣu iti।

Again, the superiority of Yōga (over mere renunciation) is clarified by 'bāhyasparśeṣu' verse.

kāmarahitaḥ ātmani yat sukhaṁ vindati sa eva brahmayogayuktātmā cet tadeva akṣayaṁ sukhaṁ vindati। brahmaviṣayo yogaḥ brahmayogaḥ। dhyānādiyuktasyaiva ātmasukham akṣayam। anyathā netyarthaḥ ॥21॥

The happiness experienced by one who is without desire, that same happiness in everlasting proportion without diminishing, is experienced by one who engages in 'Brahma Yōga'. Practice of Yōga on the topics concerning Brahman is 'Brahma Yōga'. By engaging in meditation (Dhyāna) alone, the happiness of self becomes everlasting and undiminishing. Otherwise not, is the meaning.