"There is only one God, but humanity calls him by many names." Rig Veda 1:164.46

"That one Being has become all this. All this is only one." Rig Veda 8:10.2

"What I am is utterly beyond your mind's ability to fully understand, therefore worship me by whatever name and form you desire. I promise that by whatever name you call upon me I will hear you and whatever form you worship me by I will bless you." Tripura Rahasya

"This universe is the outpouring of the majesty of God, the auspicious One, radiant love. Every face you see belongs to Him. He is present in everyone without exception." Yajur Veda

"Everything in the outside world changes constantly. But the Lord of Love in the inner world never changes. He rules both the inner and the outer realities. Meditate on Him. Merge in Him. Wake up from the dream that you exist apart from Him." Shvetashvatara Upanishad 1:10

"There is an eternal, all pervading intelligence in which all individual souls are rooted. That Supreme Awareness is the final truth. That is your innermost being. You are that." Chhandogya Upanishad

"There is one Supreme Controller, Who is the Inner Self of all beings. He projects Himself outward, creating infinity from the One." Katha Upanishad 2:2.12

"Vishnu's supreme form is beyond form, though all forms are projected from it. Of it the sages can only say 'It exists.' From the self-existent Lord comes this entire universe." Vishnu Purana 6:7.69-71