B.G 2.15

यं हि न व्यथयन्त्येते पुरुषं पुरुषर्षभ। समदुःखसुखं धीरं सोऽमृतत्वाय कल्पते ॥ २-१५॥

O best among men, the person who remains undisturbed by these, who is equanimous in both pain and pleasure is 'dhīra', i.e. one who possesses steadfast intellect, composure, courage, and self-control, and is indeed fit for immortality.

Gīta Bhāshya 2.15

The being is the one who is lying in the city, called 'puri', i.e. body. Because of the absence of bodily connection, one who is not perturbed at any point in time is specially called 'purusha'. How? By bravery, one can learn to react with equanimity towards pain and pleasure.

अतः प्रयोजनमाह यं हि इति॥ यम् एते मात्रास्पर्शा न व्यथयन्ति। पुरि शयमेव सन्तम्। शरीरसम्बन्धाभावे सर्वेषामपि व्यथाभावात् पुरुषम् इति विशेषणम्। कथं न व्यथयन्ति? समदुःखसुखत्वात्। तत्कथम्? धैर्येण ॥ १५ ॥

Its (overcoming self-attachment) practical use is stated by 'yam hi' verse. The person referred here is the one who does not get perturbed by the contact of sensations. The being is the one who is lying in the city, called 'puri' i.e. body. Because of the absence of bodily connection, one who is not perturbed all the time is specially called 'purusha'. How can one overcome this disturbance? Having equanimity towards pain and pleasure. How? By bravery.

Gīta Tātparya 2.15

One can defeat death only by becoming 'purusha', i.e., understanding auspicious qualities of the Lord.

फलमाह। यं हीति। न केवलमव्यथामात्रेणामृतत्वं किन्तु पुरुषम्।

The benefit (of enduring pleasure and pain with equanimity) is described in 'yam hi' verse. One cannot defeat death just by getting rid of misery. One can defeat it by becoming 'purusha'.

"पुरु ब्रह्म गुणाधिक्यात् तज्ज्ञानात्पुरुषः स्मृतः"

"Brahman is called 'pura' because of increased auspicious qualities. One who has such knowledge of Brahman is called 'Purusha'".

इति प्रवृत्ते।

–thus states the ancient text Pravrutti.

पुरुसरणात् पुरुष इत्यर्थः ॥१५॥

'Purusha' means one who goes after the knowledge of auspicious qualities of the Purusha.