Maitri (Maitrāyaṇīya) Upaniṣad 2.4

2.4

yo ha khalu vācoparisthaḥ śrūyate sa eva vā eṣa śuddhaḥ pūtaḥ śūnyaḥ śānto prāṇo'nīśatmā'nanto'kṣayyaḥ sthiraḥ śāśvato'jaḥ svatantraḥ sve mahimni tiṣṭhatyanenedaṃ śarīraṃ cetanavatpratiṣṭhāpitaṃ pracodayitā caiṣo'syeti te hocurbhagavankathamanenedṛśenānicchenaitadvidhamidaṃ cetanavatpratiṣṭhāpitaṃ pracodayitā caiṣo'syeti kathamiti tānhovāca ||

4. “He, assuredly, indeed, who is reputed as standing aloof, like those who, among qualities, abstain from intercourse with them—He, verily, is pure, clean, void, tranquil, breathless, selfless, endless, undecaying, steadfast, eternal, unborn, independent. He abides in his own greatness. By him this body is set up in possession of intelligence; or, in other words, this very one, verily, is its driver.”

Then they said: “Sir, how by this kind of indifferent being is this sort of thing set up in possession of intelligence? Or, in other words, how is this one its driver?”

Then he said to them:—