Darshana Upanishad 237

237

nādābhivyaktirityetaccihnaṃ tatsiddhisūcakam |
yāvadetāni saṃpaśyet tāvadevaṃ samācaret || 12 ||

and the manifestation of the [inner] sound—this is the sign indicative of its success. / As long as one observes these, for so long should one practice thus. || 12