Yāska's Nirukta 17.9

17.9

“upasannāya tu nirbrūyāt yo vā'laṃ vijñātuṃ syānmedhāvine tapasvine vā” | ya eva tu medhāvī syāt-anyajanmāntarānubhāvitayā prajñayā yuktaḥ, yo vā tapasvī, kāmaṃ tābhyāmavaiyākaraṇābhyāmapi nirbrūyādeva, na hi tayorasādhyaṃ kiñcidasti, tapasā hi svayamapi vedārthaḥ prādurbhavedeva | yathā mantrāḥ prādurabhavan pūrveṣāmṛṣīṇām| medhāvyapi ca svayamapyutprekṣituṃ śaknuyāt, kimutāṃcyamānamavaboddhum | yo vānyaḥ kaścidalaṃ paryāp‍to vijñātumetacchāstraṃ bhavet, dṛḍhagrāhī sthirabuddhiḥ, tasmai nirbrūyādeva sarvathā yatātmane viditavedāṅgāya vedārthe brāhmaṇāya | anupasannāya naiva nirbrūyāt, yadyapi tapasvī, medhāvī, dṛḍhagrāhī vā || uktaṃ hi“yaścānyāyena nirbrūyādyaścānyāyena pṛcchati | tayoranyataro mṛtyuṃ vidveṣaṃ vā'dhigacchati” || iti |