अशोच्यानन्वशोचस्त्वं प्रज्ञावादांश्च भाषसे।गतासूनगतासूंश्च नानुशोचन्ति पण्डिताः॥
aśocyān-anvaśocas-tvaṃ prajñā-vādānś ca bhāṣasegatāsūn-agatāsūnś-ca nānuśocanti paṇḍitāḥ
Word by word
The verse says
Krishna said: You grieve for those who need no grieving, and you talk like a wise man while you do it. The wise do not mourn — not for the living, and not for the dead.
In plain words
The teaching begins, and the first thing it does is take Arjuna's speech apart.
Two charges. You are grieving for people who do not need it. And you are dressing that grief in the language of wisdom.
That second one is sharp. Krishna heard the five verses of borrowed doctrine at the end of Chapter 1. He is telling Arjuna that he noticed.
Where you've felt this · at work
Someone explains at length why they cannot do a thing, and the reasons are all sound. You can still hear that the reasons came after the decision. They are not lying. They just built the case backwards.
Going deeper
Prajñā-vādān bhāṣase — you speak the words of wisdom. It is not a compliment.
The Gita has a steady interest in the difference between knowing a thing and saying it. Arjuna's speech about family duty and fallen ancestors was technically correct doctrine, delivered by a man who admitted at the end that he had only heard it. Krishna's reply names the gap between the two.
Then the claim itself, which is deliberately strange: the wise mourn neither the dead nor the living. The dead you might expect. Why the living?
Because the same thing is true of both. What Arjuna is grieving over — that these people will stop existing — was never the situation. The part that could end was always ending; the part that matters does not.
That is the whole argument of the next ten verses, stated before it is proved. It is worth noticing that Krishna makes the claim first and supports it afterwards. He is not reasoning his way toward a conclusion. He is describing something he can see, and then explaining it.