Bhagavad Gita 17.11

अफलाकाङ्क्षिभिर्यज्ञो विधिदृष्टो य इज्यते।यष्टव्यमेवेति मनः समाधाय स सात्त्विकः॥

aphalākāṅkṣibhiryajño vidhidṛṣṭo ya ijyate |yaṣṭavyameveti manaḥ samādhāya sa sāttvikaḥ ||

That sacrifice which is offered by men without desire for reward, as enjoined by the ordinance (scripture), with a firm faith that doing so is their duty, is Sattvic or pure.

Sacrifice is pure when it is offered by one who does not covet the fruit of it, when it is done according to the commands of scripture, and with implicit faith that the sacrifice is a duty.

Our plain-language meaning of this verse is waiting for scholar review.