Bhagavad Gita 2.15
यं हि न व्यथयन्त्येते पुरुषं पुरुषर्षभ। समदुःखसुखं धीरं सोऽमृतत्वाय कल्पते।।2.15।।
yaṃ hi na vyathayantyete puruṣaṃ puruṣarṣabha| samaduḥkhasukhaṃ dhīraṃ so'mṛtatvāya kalpate||2.15||
yam hi na vyathayantyete purusham purusharshabha samaduhkhasukham dhiram so'mritatvaya kalpate2.15
Meaning
The person whom these dualities of pleasure and pain do not disturb, who remains steady and balanced in both — that wise person becomes fit for immortality.
हे पुरुषश्रेष्ठ! जिस धीर पुरुष को ये (सुख-दुख) व्यथित नहीं करते और जो सुख-दुख में समभाव रखता है, वह मोक्ष के योग्य होता है।
This is verse 15 of 72 in Chapter 2 (Sankhya Yoga) of the Bhagavad Gita.