Bhagavad Gita Chapter 4, Verse 2

एवं परम्पराप्राप्तमिमं राजर्षयो विदुः | स कालेनेह महता योगो नष्टः परन्तप ||

evaṁ paramparā-prāptam imaṁ rājarṣayo viduḥ sa kāleneha mahatā yogo naṣṭaḥ parantapa

The Blessed Lord said: This yoga was thus received by the royal sages in succession. But with the long passage of time, this yoga has been lost here, O Parantapa (scorcher of foes).

Krishna explains the tragic break in the teaching lineage. The yoga (avyayam—imperishable) that was passed down through generations of royal sages (rājarṣayaḥ) eventually became lost (naṣṭaḥ) over vast time (mahatā kālena). This verse reveals why Krishna must teach it again: the chain broke. The teaching itself is eternal, but human transmission can be interrupted. This establishes the urgency—Arjuna isn't just learning an ancient teaching; he's receiving it at a moment when it had been forgotten. The word 'parantapa' (scorcher of foes) addresses Arjuna directly, emphasizing this is personal, immediate teaching, not abstract philosophy.