Bhagavad Gita · 18.26

मुक्तसङ्गोऽनहंवादी धृत्युत्साहसमन्वितः।सिद्ध्यसिद्ध्योर्निर्विकारः कर्ता सात्त्विक उच्यते॥

mukta-saṅgo 'nahaṁ-vādī dhṛity-utsāha-samanvitaḥ siddhyasiddhyor nirvikāraḥ kartā sāttvika uchyate

The doer who is free from attachment, non-egoistic, endowed with determination and enthusiasm, and unaffected by success or failure — is said to be sattvic.

— Bhagavad Gita 18.26

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