Chapter 6 of BhAgavad GitA (BG) is titled ‘Yoga of Meditation’. Though the words used are yoga and meditation, it does not refer to yogic meditation; it is Vedantic meditation. Sutra 2 of Patanjali yoga sutras is ‘yoga chittavritti nirodha’ meaning yoga is the cessation of vritties of mind (modifications of mind). It is a state of thoughtlessness so to speak. Vedantic meditation does not require cessation of the vritties. Instead, it is about atma-vritti. The yogic meditation is useful for it enables the mind to quieten so as to undertake Vedantic meditation. Verses 20 to 23 of chapter 6 talk about the two types of meditation and the benefits flowing from the Vedantic meditation. The website https://www.gitasupersite.iitk.ac.in/ has BG and other scriptures in different languages with their meanings and commentaries. There are lectures of Swami ParmArthananda on Gita BhAsyama of Shankaracharya available on the website of Arsha Avinash Foundation (https://arshaavinash.in/).

The four verses, their meanings, and explanations

यत्रोपरमते चित्तं निरुद्धं योगसेवया।
यत्र चैवात्मनाऽऽत्मानं पश्यन्नात्मनि तुष्यति।।6.20।।
yatrōparamatē cittaṅ niruddhaṅ yōgasēvayā.
yatra caivātmanā৷৷tmānaṅ paśyannātmani tuṣyati৷৷6.20৷৷

Meaning: When the mind comes to rest, restrained by the practice of yoga, and when beholding the Self, by the Self, he is content in the Self.

Explanation: Practice of yoga means yogic meditation to quieten the mind. A person with a quietened mind is able to do Vedantic meditation to abide and be established in the Self. As he has already completed sravan and manan, abiding is at a subtle level of intellect. The person thinks in a focused (meditative) way about Vedantic teachings, in particular, that ‘I am Brahman’. He is convinced to claim Selfhood. As the Brahman is infinite and complete, the person is possessed of completeness and contentment.

सुखमात्यन्तिकं यत्तद्बुद्धिग्राह्यमतीन्द्रियम्।
वेत्ति यत्र न चैवायं स्थितश्चलति तत्त्वतः।।6.21।।
sukhamātyantikaṅ yattadbuddhigrāhyamatīndriyam.
vētti yatra na caivāyaṅ sthitaścalati tattvataḥ৷৷6.21৷৷

Meaning: He knows that infinite happiness is grasped by the intellect and transcends the senses. Thus established, he does not deviate from the truth.

Explanation: This verse clears a common misconception about happiness. The person established in the Self knows that he is purnam (complete). The other name of purnam is happiness. This happiness is not experienceable happiness. The verse makes it clear that happiness is grasped by the intellect. It is beyond the senses meaning that it is beyond any experience. Therefore, it is different from the happiness of yogic samadhi. As happiness is the outcome of knowledge, it is always available. It does not depend on external conditions. All other happiness that is experienced trickle from it. The person so established knows the truth of his Selfhood.

यं लब्ध्वा चापरं लाभं मन्यते नाधिकं ततः।
यस्मिन्स्थितो न दुःखेन गुरुणापि विचाल्यते।।6.22।।
yaṅ labdhvā cāparaṅ lābhaṅ manyatē nādhikaṅ tataḥ.
yasminsthitō na duḥkhēna guruṇāpi vicālyatē৷৷6.22৷৷

Meaning: Having attained this, no greater gain can he imagine; established in this, he is not moved even by profound sorrow.

Explanation: Being established in the Self, he is at the summit, he is devoid of any longing. He is anandaswarupam. This is the greatest happiness because it does not depend on place, time, and object. It is always available whereas all other types of happiness are fleeting. He is not affected by worldly sorrows because they are mithyA belonging to a lower order of reality. No doubt, he deals with them at the empirical (mithyA) level. The sorrow is mithyA, his effort to deal with them is mithyA, and result, whether success or failure is also mithyA. He, as the Self, is detached and unaffected. There is a talk by Swami Sarvapriyananda on this verse under the title ‘No Greater Gain’ available on Youtube (https://www.youtube.com/watch?v=yr9E3AKzEJk).
The Swami also talks in the context of purnamadam of Isha Upanishad.

तं विद्याद् दुःखसंयोगवियोगं योगसंज्ञितम्।
स निश्चयेन योक्तव्यो योगोऽनिर्विण्णचेतसा।।6.23।।
taṅ vidyād duḥkhasaṅyōgaviyōgaṅ yōgasaṅjñitam.
sa niścayēna yōktavyō yōgō.nirviṇṇacētasā৷৷6.23৷৷

Meaning: Let this, the dissolution of the union with pain, be known as yoga; this yoga is to be practiced with determination and with an undismayed mind.

Explanation: The verse redefines yoga in a different manner. Yoga means union. But here it refers to separation from union with pain. Though our real nature is happiness (Anandaswarupam), our normal condition is that very often we get ‘united’ with sorrow due to the veil of mAyA (ignorance). This union with sorrow is to be broken by reclaiming our true nature by Self-knowledge. In the present condition, there is union, and then there is separation. It is a yoga of separation. It is yoga for it has to be practiced with patience for a long time with a focussed mind. There will be obstacles but the mind should not be defeatist.