Praśna Upaniṣad ("Six Questions") 6.4.p1

6.4.p1

sa yathemā nadyaḥ syandamānāḥ samudrāyaṇāḥ samudraṃ prāpyāstaṃ gacchanti bhidyete
tāsāṃ nāmarūpe samudra ityevaṃ procyate

5. As these flowing rivers that tend toward the ocean, on reaching the ocean, disappear, their name and form (nāma-rūpa) are destroyed, and it is called simply "the ocean"—even so of this spectator these sixteen parts that tend toward the Person, on reaching the Person, disappear, their name and form are destroyed, and it is called simply "the Person." That one continues without parts, immortal! As to that there is this verse:—