Bhagavad Gita 3.19

Therefore, do your duty perfectly, without worrying about the results, for he who does his duty without attachment attains the Supreme.

तस्मादसक्तः सततं कार्यं कर्म समाचर।
असक्तो ह्याचरन्कर्म परमाप्नोति पूरुषः॥

tasmādasaktaḥ satataṃ kāryaṃ karma samācara|
asakto hyācarankarma paramāpnoti pūruṣaḥ||

English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).