Bhagavad Gita Chapter 15, Verse 20

इति गुह्यतमं शास्त्रमिदमुक्तं मयानघ | एतद् बुद्ध्वा बुद्धिमान्स्यात्कृतकृत्यश्च भारत ||

iti guhyatamaṁ śāstram idam uktaṁ mayānagha etad buddhvā buddhimān syāt kṛta-kṛtyaś ca bhārata

Thus, this most secret scripture has been spoken by Me, O sinless one. Having understood this, one becomes wise and accomplishes all duties, O Arjuna.

Krishna concludes Chapter 15: 'Iti guhyatamaṁ śāstram idam uktaṁ mayānagha'—thus, this most secret scripture has been spoken by Me. This is 'guhyatamam'—the most secret, the most confidential teaching. Chapter 15 contains the deepest secrets: the ashvattha tree, the living entity, Purushottama. This isn't just information—it's the most secret knowledge. 'Etad buddhvā buddhimān syāt kṛta-kṛtyaś ca'—having understood this, one becomes wise and accomplishes all duties. Understanding this teaching makes you wise—not just knowledgeable, but truly wise. And it makes you 'kṛta-kṛtyaḥ'—one whose duties are accomplished. This doesn't mean you stop doing duties—it means you understand the purpose of all duties (knowing Purushottama), and thus all duties are fulfilled. This is the conclusion: understanding Chapter 15's secret knowledge makes you wise and fulfills all your duties. The chapter ends with this promise: understand Purushottama, and you become wise and accomplish everything.