Advaita Vedānta

The yoga in question is the yoga of even or equal vision, understood as the restraint of all mind-movement so that the mind rests in the attributeless. One source describes it as the cancelling of attachment, aversion and the rest in the mind, the very things that produce uneven vision, so that an even seeing is everywhere; the firm footing Arjuna misses is the steady abiding of this restrained mind. Another notes that Arjuna, having heard that the mind is fickle, supposes that steadiness in the attributeless is hard and so asks for the means; the objection that restraint should still accomplish it is met by 'it is well known' that the mind is restless. Another reads the equal-yoga as preceded by sannyasa, renunciation, with non-injury as its leading mark.

Śaṅkarācārya · Śrī Ānandagiri · Madhusūdana Sarasvatī · Śrī Nīlakaṇṭha · Dhanapati Sūri

Viśiṣṭādvaita

The equality is given a precise content: it is the seeing-alike of selves that had been experienced as utterly distinct by the differences of god, man, and the rest, and by the difference of soul and Lord. They are seen as alike because each has knowledge for its single defining form, and so they resemble one another; and they are seen as like the Lord in that, freed from action, they share his nature. This equality rests on knowledge-only-form, on faultlessness, and on connection with Brahman and the Lord's qualities while disconnected from all else. Arjuna's doubt is whether this inwardly consummated vision can stand fast in him, given the mind's restlessness, agitation, strength and stubbornness, which make it as hard to hold back as the wind.

Rāmānujācārya · Vedānta Deśika

Dvaita

What Arjuna cannot see a firm standing for is the yoga itself. There is a grammatical care here: since both equality and yoga were the topic, the pronoun 'of this' is ambiguous, but it is resolved to yoga, because yoga is the principal topic while equality is subordinate (expressed by the instrumental case), and because 'because of its restlessness' has no other subject available except, by the next sentence, the mind. So the verse states plainly that the firm standing of this yoga is not seen, the mind being unsteady.

Madhvācārya · Śrī Jayatīrtha

Śuddhādvaita

Arjuna thinks the yoga as defined is impossible, since the very restraint, nirodha, of the citta that the evenness requires runs up against a mind whose nature is to be moved. One source reads the doubt not as mere weakness but as a genuine recognition that self-reliant restraint-discipline fails against such a mind, and that this very failure is where the door for grace opens; he cites the well-known losses of yoga in the cases of Agnidhra, Saubhari and others, and the image that holding in the wind, which shakes this way and that in the sky, into pots is hard, just as this is. Another grounds the doubt in two causes together: Arjuna is filled with the egoism of self-claim and the mind itself wavers, so he cannot see the unwavering stability of the yoga of sameness in happiness, suffering and self toward all.

Vallabhācārya · Śrī Puruṣottama

Bhedabheda

The reading is straightforward: the yoga declared by the Lord has no steady foundation that Arjuna can see, because of the restlessness of the mind, and the following verse is cited as the warrant, that the mind is restless, turbulent, strong and unyielding, its restraint as hard as that of the wind.

Śrī Bhāskara

Kashmir Shaivism

Attention falls on the two pronouns. 'Which' is indirect in what it denotes and 'this' is direct, and together they hint that Brahman, though made plain by the succession of means just taught and pointed out directly, yet stands very far off and so becomes a thing only indirectly reached, because of the wicked unsteadiness of the mind. The mind 'churns', powerfully able to disturb both the seen and the unseen; and 'firm' is read here as 'hard to ward off from its evil working', so the very stability in question is the mind's stubborn persistence in disturbance.

Ācārya Abhinavagupta

Bhakti

These commentators read the yoga as the mind, free of laya (dullness) and vikshepa (distraction), standing in the single form of the atma, for which Arjuna sees no lasting standing because the mind is unsteady by nature. Two of them sharpen the difficulty with a concrete content of the sameness: it would require seeing the happiness and suffering of all beings as equal to one's own. Toward kinsmen and the indifferent such sameness might arise, but toward foes, slayers, haters and revilers it could never come; Arjuna cannot see his own, Yudhishthira's, and Duryodhana's happiness and suffering as equal. And even granting the discrimination that self, Supreme Self, vital airs, senses and bodily elements are alike in oneself and one's foes, the evenness still would not last, lasting only two or three or four days, because the powerful and restless mind cannot be restrained by that discrimination; rather the discrimination itself is swallowed up by the mind attached to sense objects. One source renders the whole as Arjuna's heartfelt cry that the mind, like a monkey or a storm, rushes out when curbed and gains vigor from every attempt to restrain it, so that steadiness, and then evenness, seldom comes.

Śrīdhara Svāmī · Śrīla Viśvanātha · Śrīla Baladeva · Sant Jñāneśvar

Modern

One modern voice voices the difficulty plainly: the mind is restless, impetuous and unsteady, so steady concentration is hard and the mind wanders in the twinkling of an eye. Another reads the 'yoga of samya' specifically as Karma-Yoga, acquired by equability of reason, and reports Arjuna's doubt that such a yoga will last permanently given the mind's inconstancy. A third sets the verse in the chapter's flow: from verse 2.38 onward the Lord taught that keeping samata, evenness, in the chitta regarding gain and loss and pleasure and pain frees one from the binding of karmas, and called this karma-phala-tyaga the perfection, samata; the verses on dhyana-yoga from the tenth to the thirty-second described how to gain it, and now, with his eye on that whole description, Arjuna brings out his own opinion and difficulty.

Swami Sivananda · Lokmanya Tilak · Swami Ramsukhdas