Bhagavad Gita Chapter 4, Verse 15

एवं ज्ञात्वा कृतं कर्म पूर्वैरपि मुमुक्षुभिः | कुरु कर्मैव तस्मात्त्वं पूर्वैः पूर्वतरं कृतम् ||

evaṁ jñātvā kṛtaṁ karma pūrvair api mumukṣubhiḥ kuru karmaiva tasmāt tvaṁ pūrvaiḥ pūrvataraṁ kṛtam

Having known this, the ancient seekers of liberation performed action. Therefore, you should also perform action, just as the ancients did in days of old.

Krishna reinforces the teaching through historical precedent. 'Pūrvair mumukṣubhiḥ' (ancient seekers of liberation) performed action ('karma kṛtam') after understanding this truth ('evaṁ jñātvā'). This connects back to verses 4.1-4.2—the ancient lineage knew this teaching. The instruction 'kuru karmaiva' (you too should perform action) is direct: Arjuna must act, just as ancient sages acted. The phrase 'pūrvaiḥ pūrvataraṁ kṛtam' (done by even more ancient ones) emphasizes this isn't new—it's time-tested. This verse completes the answer to Arjuna's question from Chapter 3: action is necessary, but must be done with understanding (action without attachment). The closing of this section sets up verses 4.16-4.42, which will explore the nature of action in detail.