Shvetashvatara Upanishad, 2.9.
The soul is born and unfolds in a body, with dreams and desires and the food of life. And then it is reborn in new bodies in accordance with its former works. The quality of the soul determines its future body--earthly or airy, heavy or light.
Shvetashvatara Upanishad, 5.11-12
Than whom there is naught else higher, than whom there is naught smaller, naught greater, the One stands like a tree established in heaven. By Him, the Person, is this whole universe filled.
Shvetashvatara Upanishad 3.9