Bhagavad Gita 17.11

अफलाकाङ्क्षिभिर्यज्ञो विधिदृष्टो य इज्यते |
यष्टव्यमेवेति मनः समाधाय स सात्त्विकः

Translation

Sacrifice that is performed according to scriptural injunctions without expectation of rewards, with the firm conviction of the mind that it is a matter of duty, is of the nature of goodness.