Shri Shankaracharya on the importance of Self-realisation

"Let people quote the Scriptures and sacrifice to the gods,
let them perform rituals and worship the deities,
but there is no Liberation without the realisation of one’s identity with the Self,
no, not even in the lifetime of a hundred Brahmas put together."

- Shri Shankaracharya, Viveka Chudamani (8th Century CE but possibly 1000 years earlier)

Shri Shankaracharya's Viveka Chudamani (which translates as: The Crest Jewel of Discrimination) expounds the significance of Self-Realisation and the ways to attain it, methods of meditation (dhyana) and introspection of the Atman (Self). It concludes with the denial of Pluralism of Self, and the description of the state of Self-Realisation.

A jewel is symbolic of the Non-dual Self,
which is both single and at the same time multifaceted.