तस्मात्त्वमुत्तिष्ठ यशो लभस्व जित्वा शत्रून् भुङ्क्ष्व राज्यं समृद्धम्।मयैवैते निहताः पूर्वमेव निमित्तमात्रं भव सव्यसाचिन्॥
tasmāt tvam uttiṣṭha yaśo labhasvajitvā śatrūn bhuṅkṣva rājyaṃ samṛddhammayaivaite nihatāḥ pūrvam evanimitta-mātraṃ bhava savya-sācin
Word by word
The verse says
So stand up, win fame, defeat your enemies, enjoy a prosperous kingdom. They have already been struck down by me. Be the occasion only, left-handed archer.
In plain words
Nimitta-mātram — the occasion only. The instrument, nothing more.
This is the answer to the question Arjuna asked in Chapter 1, and it is not comforting in the way he wanted.
He is not told that nobody will die. He is told that it is not his doing.
Where you've felt this · at work
You are the one who has to tell a colleague that his project has been cancelled. You did not decide it, you argued against it, and you are the person in the room when he finds out. For the rest of his time there, some part of him associates you with that afternoon.
Going deeper
Being the occasion of something is a real position, and the verse neither inflates nor dismisses it.
Nimitta names the thing through which something happens, as distinct from the thing that makes it happen. Arjuna will fire the arrows. The outcome was not produced by his decision to fire them, and would not be prevented by his deciding not to.
The traditions have argued about this for a very long time, and the argument is not silly. Read carelessly, the verse excuses anything: the agent is only an instrument, so nothing is his fault.
What holds against that reading is everything the book has already said. Eighteen chapters are spent telling Arjuna how to act well, which would be pointless if his actions were empty. The claim is narrower: you are responsible for how you act, and you were never the author of whether the world turns. Those are different questions, and most of the suffering in this book comes from a man answering the second one as though it were the first.