Brahma Sutras
ॐ पुरुषार्थोऽतः शब्दादिति बादरायणः ॐ ॥ ३-४-१॥
Badarayana thinks that liberation results from this (knowledge of the Self), (as presented in the Upanishads), because the Vedic texts declare so.
english translation
OM puruSArtho'taH zabdAditi bAdarAyaNaH OM ॥ 3-4-1॥
hk transliteration by Sanscript