Bhagavad Gita Chapter 18, Verse 75

व्यासप्रसादाच्छ्रुतवानेतद्गुह्यमहं परम् | योगं योगेश्वरात्कृष्णात्साक्षात्कथयतः स्वयम् ||

vyāsa-prasādāc chrutavān etad guhyam ahaṁ param yogaṁ yogeśvarāt kṛṣṇāt sākṣāt kathayataḥ svayam

By the grace of Vyasa, I have heard this supreme secret yoga directly from the Lord of yoga, Krishna, speaking it Himself.

Sanjaya explains how he received this knowledge. 'Vyāsa-prasādāc chrutavān etad guhyam ahaṁ param'—by the grace of Vyasa (vyāsa-prasādāt), I (aham) have heard (śrutavān) this supreme secret (etat guhyam param) yoga. 'Yogaṁ yogeśvarāt kṛṣṇāt sākṣāt kathayataḥ svayam'—the yoga (yogam) from the Lord of yoga (yogeśvarāt), from Krishna (kṛṣṇāt), speaking it Himself (sākṣāt kathayataḥ svayam). This reveals how Sanjaya received the divine vision to see and hear the conversation between Krishna and Arjuna. It was through the grace of Vyasa (the sage who compiled the Mahabharata) that Sanjaya was granted this ability. Sanjaya heard this supreme secret yoga directly from Krishna Himself, the Lord of yoga. This emphasizes the divine nature of the teaching and the special privilege of receiving it directly.