Brihadaranyaka Upanishad 4.3.32

4.3.32

salila eko draṣṭādvaito bhavatyeṣa brahmalokaḥ samrāḍiti hainamanuśaśāsa yājñavalkya eṣāsya paramā gatireṣāsya paramā saṃpadeṣo'sya paramo loka eṣo'sya parama ānanda etasyaivānandasyānyāni bhūtāni mātrāmupajīvanti

'An ocean is that one seer, without any duality; this is the Brahma-world, O King.' Thus did Yâgñavalkya teach him. This is his highest goal, this is his highest Success, this is his highest world, this is his highest bliss. All other creatures live on a small portion of that bliss.