B.G 6.20,22, and 23

yatroparamate cittaṁ niruddhaṁ yogasevayā। yatra caivātmanā'tmānaṁ paśyannātmani tuṣyati ॥20॥

sukhamātyantikaṁ yattad buddhigrāhyamatīṁdriyam। vetti yatra na caivāyaṁ sthitaścalati tattvataḥ ॥21॥

yaṁ labdhvā cāparaṁ lābhaṁ manyate nādhikaṁ tataḥ। yasmin sthito na duḥkhena guruṇāpi vicālyate ॥22॥

taṁ vidyād duḥkhasaṁyogaviyogaṁ yogasañjñitam। sa niścayena yoktavyo yogo nirviṇṇacetasā ॥23॥

Where the mind is restrained by the practice of Yoga and stationed in the supreme, where indeed, seeing the lord through the mind, becomes satisfied within the body. The intellect perceives that supreme happiness which is beyond the senses, and understanding him as such doesn't vacillate from the situated true form of the Lord. Having achieved such a state, he considers no other gain as superior, and having situated there, is not disturbed by even the heaviest sorrow. Know that be Yoga which removes association or disassociation of misery, i.e. which allows one to transcend the misery. This yoga should be practiced with determination by one with a detached mind.

Gīta Tātparya 6.20-23

'ātmānam' - Lord Vishnu; 'ātmanā' - by His grace.

ātmānaṁ viṣṇum। ātmanā tatprasādena ॥20॥

The word 'ātmānam' refers to Lord Vishnu. The word 'ātmanā' means 'by His grace'.