In plain words
Arjuna, one who, using oneself as the measure, sees happiness and suffering alike everywhere is regarded by Me as the highest yogin.
Word for word
Who sees everywhere, by the measure of oneself, happiness and whatever pain alike, O Arjuna, he [is] held the highest yogin.
The commentators
Bhagavadgītābhāṣyam
किञ्च अन्यत् —
आत्मौपम्येन आत्मा स्वयमेव उपमीयते अनया इत्युपमा तस्या उपमाया भावः औपम्यं तेन आत्मौपम्येन, सर्वत्र सर्वभूतेषु समं तुल्यं पश्यति यः अर्जुन, स च किं समं पश्यति इत्युच्यते — यथा मम सुखम् इष्टं तथा सर्वप्राणिनां सुखम् अनुकूलम् । वाशब्दः चार्थे । यदि वा यच्च दुःखं मम प्रतिकूलम् अनिष्टं यथा तथा सर्वप्राणिनां दुःखम् अनिष्टं प्रतिकूलं इत्येवम् आत्मौपम्येन सुखदुःखे अनुकूलप्रतिकूले तुल्यतया सर्वभूतेषु समं पश्यति, न कस्यचित् प्रतिकूलमाचरति, अहिंसक इत्यर्थः । यः एवमहिंसकः सम्यग्दर्शननिष्ठः स योगी परमः उत्कृष्टः मतः अभिप्रेतः सर्वयोगिनां मध्ये ॥ ३२ ॥
In plain words
And there is something further —
‘By comparison with oneself’ means measuring by yourself, using your own case as the standard—that comparison, that quality of comparability, is what's meant here. Whoever sees the same thing everywhere, in every being, equally, Arjuna—and what does he see as the same? Just as my own happiness is something I want, so happiness is welcome to every living creature. Or, whatever sorrow is unwelcome and unwanted to me, sorrow is just as unwanted and unwelcome to every living creature. Seeing this way, by comparison with himself, he regards happiness and sorrow, the welcome and the unwelcome, with equal eyes in every being—and treats no one with hostility. That is what ‘non-violent’ means. Whoever is non-violent in this way, established firmly in right vision, is the supreme yogī—regarded, among all yogīs, as the very best.
Close to the Sanskrit
And what else — another thing —
‘By comparison with oneself’—oneself, indeed, is compared by this—thus ‘comparison’; the state of that comparison is ‘comparability’; by that comparison with oneself. Whoever sees, everywhere, in all beings, equal—i.e. equivalent, O Arjuna—and what does he see as equal? It is explained: just as my happiness is desired, so happiness is agreeable to all living beings. The word ‘vā’ is used in the sense of ‘and’. Or, whatever sorrow is disagreeable, undesired, to me, so sorrow is undesired, disagreeable, to all living beings—in this way, by comparison with oneself, in happiness and sorrow, agreeable and disagreeable, with equal regard, in all beings, he sees equally; he does nothing adverse to anyone—that is ‘non-violent’—that is the meaning. Whoever, thus non-violent, established in right vision—he is the supreme yogī, i.e. the foremost, is considered, i.e. regarded as such, among all yogīs.
Gītā Vāhini
“యోగాభ్యాసము చేయువాని చిత్తము గాలిలేని స్థానమున దీపము ఉండినట్లు నిశ్చలముగా ఉండవలెను. ఏ ఏ సమయమున మనస్సు చలించునో అప్పటికప్పుడే దానిని నిశ్చలముగా, పరుగెత్తనీయక అరికట్టుటకు ప్రయత్నించవలెను. అన్నింటియందూ నేనే యున్నానను భావమును, సర్వభూతములూ నాయందే యున్నవను ఏకత్వమునూ పొందువాడు అన్ని యోగములనూ సాధించినవాడగును. అట్టివానికి పరులనియూ, పరమాత్మ అనియూ భేదము లేకుండును. ఇతరుల సుఖదుఃఖములు తనవిగా భావించును. ఇతర హృదయములను బాధింపజేయక సర్వులనూ సర్వేశ్వర భావమున ప్రేమించును. ఇట్టి భావము గలవాడు యోగులలో శ్రేష్ఠుడు” అని భగవంతుడైన కృష్ణుడు భక్తుడైన అర్జునునకు తెలుపుచుండగా, మధ్యలో అర్జునుడు సందేహ మనస్కుడై సమాధాన మడుగుచున్నాడు.
In plain words
“The citta of one who practises yoga must be as steady as a lamp in a windless place. Whenever the Manas wavers, one must strive right then to restrain it, holding it steady and not letting it run. He who attains the feeling “I alone am present in everything” and the oneness “all beings are in me alone” has accomplished all yogas. For such a one there is no distinction between “others” and “Paramātma”. He regards the joys and sorrows of others as his own. Never causing pain to another's heart, he loves all, seeing them as the Lord of all. He who has such a feeling is the best among yogis.” As Kṛṣṇa, who is God, was teaching this to Arjuna, the devotee, Arjuna, his mind in doubt, asks in the middle for an answer.