One verse

Bhagavad Gita 4.2

4.2

एवं परम्पराप्राप्तमिमं राजर्षयो विदुः | स कालेनेह महता योगो नष्टः परन्तप ||४-२||

evaṃ paramparāprāptamimaṃ rājarṣayo viduḥ . sa kāleneha mahatā yogo naṣṭaḥ parantapa ||4-2||

evam
thus
paramparā
by disciplic succession
prāptam
received
imam
this science
rāja-ṛṣayaḥ
the saintly kings
viduḥ
understood
saḥ
that knowledge
kālena
in the course of time
iha
in this world
mahatā
great
yogaḥ
the science of one’s relationship with the Supreme
naṣṭaḥ
scattered
param-tapa
O Arjuna, subduer of the enemies
saḥ
the same

This supreme science was thus received through the chain of disciplic succession, and the saintly kings understood it in that way. But in course of time the succession was broken, and therefore the science as it is appears to be lost.