Bhagavad Gita 18.10
The wise man who has attained purity, whose doubts are resolved, who is filled with the spirit of self-abnegation, does not shy away from action due to its pain, nor does he crave it due to its pleasure.
न द्वेष्ट्यकुशलं कर्म कुशले नानुषज्जते।त्यागी सत्त्वसमाविष्टो मेधावी छिन्नसंशयः॥na dveṣṭyakuśalaṃ karma kuśale nānuṣajjate|tyāgī sattvasamāviṣṭo medhāvī chinnasaṃśayaḥ||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).