Śāṅkhāyana (Kauṣītaki) Āraṇyaka 8.6

8.6

ŚĀ 8,6
yas tityāja sacividaṃ sakhāyaṃ na tasya vācy api bhāgo asti | yad īṃ śṛnoty alakaṃ śṛṇoti na hi praveda sukṛtasya panthām || iti | nāsyānūkte vāco bhāgo astīty eva tad āha tan na parasmā etad ahaḥ śaṃset | nāgniṃ cinuyān na mahāvratena stuyān ned ātmano 'pihīyā iti | sa yaś cāyam aśarīraḥ prajñātmā yaś cāsāv āditya ekam etad ity avocāma tau yatra vipradṛśyete ||

ŚĀ 8.6
"He who has abandoned a friend who shares knowledge / has no share even in speech. / Whatever he hears, he hears in vain; / for he does not know the path of virtuous action." / That is what it means when it says: "He has no share in speech, nor in what is recited." Therefore, one should not recite this day's [text] to another. One should not pile the fire altar, nor praise with the Mahāvrata rite, lest one be deprived of one's self. And that which we said: "That which is this bodiless conscious self and that which is yonder sun—this is one"—where they appear distinct...