Second episode/adhyaya – Sankhya yoga
avināśi tu tad viddhi
avināśi—imperishable; tu—but; tat—that; viddhi—know it; yena—by whom; sarvam—all of the body; idam—this; tatam—widespread; vināśam—destruction; avyayasya—of the imperishable; asya—of it; na kaścit—no one; kartum—to do; arhati—able.
Text Source – “http://prabhupadabooks.com/bg”
That which is widespread through out the body, know that is imperishable. Nobody can destroy the indestructible.
All of us fear death. Here Lord is saying that there is something (Soul/Consciousness) which is widespread throughout the body that is imperishable. Nobody can destroy it even if they want to, not even death. So that means what we know as “me” is still going to be there even after death. So basically Arjuna need not fear that they(Bhishma, Drona) are going die after being killed.