देही नित्यमवध्योऽयं देहे सर्वस्य भारत | तस्मात्सर्वाणि भूतानि न त्वं शोचितुमर्हसि || 30||
2.30 O Arjun, the soul that dwells within the body is immortal; therefore, you should not mourn for anyone.
Often, in the course of his teachings, Shree Krishna explains a concept in a few verses, and then states a verse summarizing those teachings. This verse is a summary of the instructions on the immortality of the self, and its distinction from the body.