Bhagavad Gita Chapter 4, Verse 3

स एवायं मया तेऽद्य योगः प्रोक्तः पुरातनः | भक्तोऽसि मे सखा चेति रहस्यं ह्येतदुत्तमम् ||

sa evāyaṁ mayā te 'dya yogaḥ proktaḥ purātanaḥ bhakto 'si me sakhā ceti rahasyaṁ hy etad uttamam

That same ancient yoga has been taught to you today by Me, for you are My devotee and My friend. This is indeed a supreme secret.

Krishna reveals why Arjuna receives this teaching: 'bhakto 'si me sakhā'—you are My devotee and My friend. This dual relationship makes Arjuna uniquely qualified. The teaching is 'rahasyaṁ uttamam'—supreme secret, not because it's hidden, but because it's only truly understood by those who approach it with both devotion (bhakta) and friendship (sakhā). The word 'purātanaḥ' (ancient) connects back to verses 4.1-4.2: this isn't new teaching, but the same eternal yoga restored. Why Arjuna? Because he combines faith with genuine relationship—he's not just a student but a friend; not just respectful but devoted. This combination opens deeper understanding.