Bhagavad Gita · 2.48

योगस्थः कुरु कर्माणि सङ्गं त्यक्त्वा धनञ्जय।सिद्ध्यसिद्ध्योः समो भूत्वा समत्वं योग उच्यते॥

yoga-sthaḥ kuru karmāṇi saṅgaṁ tyaktvā dhanañjaya siddhyasiddhyoḥ samo bhūtvā samatvaṁ yoga uchyate

Perform your duties established in yoga, O Dhananjaya, abandoning all attachment. Be equal in success and failure, for such equanimity is called yoga.

— Bhagavad Gita 2.48

Source: Sacred-Texts.com (Sanskrit) + Bhagavad-Gita.io (translations)