The Bhagavad Gita · Chapter 2 · verse 2.47
Your right is to the work itself, never to its fruits. Do not let the fruits of action be your motive, and do not be attached to inaction.
Sanskrit (Devanagari)
कर्मण्येवाधिकारस्ते मा फलेषु कदाचन। मा कर्मफलहेतुर्भूर्मा ते सङ्गोऽस्त्वकर्मणि॥
Transliteration
karmaṇy evādhikāras te mā phaleṣu kadācana; mā karma-phala-hetur bhūr mā te saṅgo 'stv akarmaṇi
English translation
Your right is to the work itself, never to its fruits. Do not let the fruits of action be your motive, and do not be attached to inaction.
Meaning — what the verse is actually saying
The single most quoted verse in the Gita and the structural core of karma yoga. You can choose the action; you cannot choose the result. Owning what you can affect, releasing what you cannot, is the entire instruction.
Modern practice — what to do today because of this
For one week, take one task per day and do it with full effort but without checking on its result. Do not refresh the email. Do not check the number. Do the work, hand it over, walk away. Notice what changes — usually the work gets better, not worse.