Bhagavad Gita 2.47
But you have only the right to work, but none to the fruit of it. Let not the fruit of your action be your motive; nor be you enamored of inaction.
कर्मण्येवाधिकारस्ते मा फलेषु कदाचन।
मा कर्मफलहेतुर्भूर्मा ते सङ्गोऽस्त्वकर्मणि॥karmaṇyevādhikāraste mā phaleṣu kadācana|
mā karmaphalaheturbhūrmā te saṅgo'stvakarmaṇi||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).