BṚHADĀRAṆYAKA UPANISHAD · 4.3.14

आरामम् अस्य पश्यन्ति न तं पश्यति कश् चनेति ।
तं नायतं बोधयेद् इत्य् आहुः ।
दुर्भिषज्यं हास्मै भवति यम् एष न प्रतिपद्यते ।
अथो खल्व् आहुर् जागरितदेश एवास्यैस इति ।
यानि ह्य् एव जाग्रत् पश्यति तानि सुप्त इति ।
अत्रायं पुरुषः स्वयंज्योतिर् भवति ।
सो ऽहं भगवते सहस्रं ददामि ।
अत ऊर्ध्वं विमोक्षाय ब्रूहीति ॥

ārāmam asya paśyanti na taṃ paśyati kaś caneti ।
taṃ nāyataṃ bodhayed ity āhuḥ ।
durbhiṣajyaṃ hāsmai bhavati yam eṣa na pratipadyate ।
atho khalv āhur jāgaritadeśa evāsyaisa iti ।
yāni hy eva jāgrat paśyati tāni supta iti ।
atrāyaṃ puruṣaḥ svayaṃjyotir bhavati ।
so ’haṃ bhagavate sahasraṃ dadāmi ।
ata ūrdhvaṃ vimokṣāya brūhīti ॥

'People may see his playground but himself no one ever sees. Therefore they say, Let no one wake a man suddenly, for it is not easy to remedy, if he does not get back (rightly to his body)." 'Here some people (object and) say: "No, this (sleep) is the same as the place of waking, for what he sees while awake, that only he sees when asleep." No, here (in sleep) the person is self-illuminated (as we explained before).' Ganaka Vaideha said: 'I give you, Sir, a thousand. Speak on for the sake of (my) emancipation.'

F. Max Müller · The Upanishads, Sacred Books of the East 15 (1884)