śravaṇᾱyᾱpi bahubhir yo na labhyaḥ
śṛṇvanto’pi bahavo yaṁ na vidyuḥ
ᾱścaryo vaktᾱ kuśalo’sya labdhᾱ
ᾱścaryo jñᾱtᾱ kuśalᾱnuśiṣṭaḥ

“To many the gift is not given to hear of the nature of the true self. Many, though they hear of the true self, do not understand it. Wonderful is he who speaks of it; intelligent is he who learns of it. Blessed is he who, taught by a good teacher, is actually able to understand it.”

– Katha Upanishad, 1.2.7