Bhagavad Gita · 16.24

तस्माच्छास्त्रं प्रमाणं ते कार्याकार्यव्यवस्थितौ।ज्ञात्वा शास्त्रविधानोक्तं कर्म कर्तुमिहार्हसि॥

tasmāch chhāstraṁ pramāṇaṁ te kāryākārya-vyavasthitau jñātvā śhāstra-vidhānoktaṁ karma kartum ihārhasi

Therefore, let the scriptures be your authority in determining what should and should not be done. Having understood what is prescribed by scriptural injunctions, you should act accordingly in this world.

— Bhagavad Gita 16.24

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