Through the grace of Vyasa I have heard this supreme and most secret Yoga direct from Krishna, the Lord of Yoga, Himself declaring it.
In simple words
Sanjaya continues: "Through the grace of the sage Vyasa, I was able to hear this supreme, most secret teaching of yoga directly from Krishna — the Lord of all yoga — as He spoke it Himself."
Word-by-word meanings
व्यासप्रसादात्through the grace of Vyasaश्रुतवान्have heardएतत्thisगुह्यम्secretअहम्Iपरम्supremeयोगम्Yogaयोगेश्वरात्from the Lord of Yogaकृष्णात्from Krishnaसाक्षात्directlyकथयतःdeclaringस्वयम्Himself
18.75 व्यासप्रसादात् through the grace of Vyasa? श्रुतवान् have heard? एतत् this? गुह्यम् secret? अहम् I? परम् supreme? योगम् Yoga? योगेश्वरात् from the Lord of Yoga? कृष्णात् from Krishna? साक्षात् directly? कथयतः declaring? स्वयम् Himself.Commentary Through the grace of Vyasa By obtaining the divine eye from him.Yoga This dialogue between Krishna and Arjuna? I have heard it direct from Him. This dialogue is called Yoga because it treats of Yoga and it leads to the attainment of union with the Lord.
Contemporary scholarly and practical interpretations for modern seekers.
This interpretation draws on a specific tradition and may not represent the view of any single school. For authoritative guidance within a specific tradition, seek a qualified teacher.
Modern
Before the great Mahabharat war commenced, the sage Vyasa had expressed his desire to grant King Dhritarashtra the boon of divine vision. However, Dhritarashtra lacked the courage to accept such a blessing. Therefore, at Dhritarashtra's request, Vyasa bestowed divine sight upon Sanjaya so that he could know the entire account of the war. Thus, Sanjaya became capable of witnessing the entire battlefield and hearing all the conversations that took place there. Seated in the magnificent royal palace, he would recount the events of the war to the blind king Dhritarashtra. Having received the precious opportunity to hear the supreme and secret knowledge through the dialogue between Sri Krishna and Arjuna, Sanjaya felt fulfilled. It is natural that he expresses his gratitude toward the accomplished sage Vyasa, the author of the Mahabharat, and bows in reverence to that incomparable seer and poet.
It is not that Sanjaya had never before heard the knowledge of the Upanishads, which would cause him to be overwhelmed with wonder on this occasion. The source of his joy was that he received such an opportunity to hear this knowledge when the Lord of Yoga, Sri Krishna Himself, was imparting this wisdom directly from His own lips.
Here, Sanjaya makes another effort to inform Dhritarashtra that Sri Krishna, the Teacher of the Gita, was not merely the son of Devaki, a cowherd boy, but rather the Almighty Supreme Being Himself. He alone had awakened Arjuna from the slumber of delusion, and He was serving as the charioteer of His devotee's chariot. He reminds the blind king that although the army of Dhritarashtra's sons was larger and better equipped with weapons and armor than the Pandava army, its destruction was inevitable, for they had to face none other than the Infinite Supreme Being Himself arrayed against them.
Sanjaya continues to speak.