Bṛhadāraṇyaka Upaniṣad ("Great Forest Teaching") 4.3.15

4.3.15

sa vā eṣa etasminsaṃprasāde ratvā caritvā dṛṣṭvaiva puṇyaṃ ca pāpaṃ ca punaḥ pratinyāyaṃ pratiyonyādravati svapnāyaiva sa yattatra kiṃcitpaśyatyananvāgatastena bhavatyasaṅgo hyayaṃ puruṣa ityevamevaitadyājñavalkya so'haṃ bhagavate sahasraṃ dadāmyata ūrdhvaṃ vimokṣāyaiva brūhīti

Yâgñavalkya said: 'That (person) having enjoyed himself in that state of bliss (samprasâda, deep sleep), having moved about and seen both good and evil, hastens back again as he came, to the place from which he started (the place of sleep), to dream. And whatever he may have seen there, he is not followed (affected) by it, for that person is not attached to anything.'
Ganaka Vaideha said: 'So it is indeed, Yâgñavalkya. I give you, Sir, a thousand. Speak on for the sake of emancipation.'