सर्वगुह्यतमं भूयः श्रृणु मे परमं वचः। इष्टोऽसि मे दृढमिति ततो वक्ष्यामि ते हितम् ॥

sarva-guhyatamaṁ bhūyaḥ śhṛiṇu me paramaṁ vachaḥ iṣhṭo ‘si me dṛiḍham iti tato vakṣhyāmi te hitam

Listen thou again to My supreme word, most secret of all; beloved art thou of Me, and steadfast of heart, therefore will I speak for thy benefit.

In plain words: Krishna asks Arjuna to listen once more to his highest and most secret teaching. He says he is sharing it because Arjuna is dearly loved and steady in heart.