Karmaṇy evādhikāras te mā phaleṣu kadācana. You have the right to work, never to its fruits. It is on office walls, desk calendars and exam halls across India.
Most people stop there, and it starts to sound like permission to stop caring about results.
The verse has two more lines. Do not make the fruit of action your motive. And the last one, the one nobody prints: mā te saṅgo ’stv akarmaṇi. Do not be attached to doing nothing either.
It is not permission to stop caring. It is an order to keep working.
Going deeper
2.47 is one verse with four parts, and the poster usually shows only the first. Kṛṣṇa says you have a right to action alone, never to its fruits. He adds that the fruit must not be your motive, and last, that you must not be attached to inaction. Read as a whole, it is a verse about working without being driven by results, and it closes the door on doing nothing. The next verse, 2.48, tells Arjuna how to do it: give up attachment, stay established in yoga, treat success and failure alike, and perform the work. Evenness of mind, it says, is yoga. The verse before, 2.46, offers an image of how little a reservoir matters to a thirsty person who already has water on every side. All of it sits in chapter 2, and what the Gītā says about purpose follows the idea further.