Many Gods, One God 

i) From Brihadaranyaka Upanishad (1.4.6--10)

This that people say: 

'Worship this God! Worship that God!' -- one god after another!  All this is his creation indeed!  And he himself is all the Gods................. He is entered in the universe even to our fingernail-tips, like a razor in a razor case, or fire in firewood.  Him those people see not, for as seen he is incomplete.  When breathing, he becomes 'breath' by name; when speaking, 'voice'; when seeing, 'the eye'; when hearing, 'the ear'; when thinking, 'the mind'; these are but the names of his acts......

"One should worship with the thought that he is one's self, for therein all become one.  This self is the footprints of that All, for by it one knows the All --just as, verily, by following a footprint one finds cattle that have been lost......One should reverence the Self alone as dear.  And he who reverences the Self alone as dear -- what he holds dear, verily, will not perish...
So whoever worships another divinity than his self, thinking, 'He is one, I am another,' knows not. He is like a sacrificial animal for the gods...."

ii) From early Gnostic Gospel According to Thomas: (99:28-30 and 95:24-28)

"I am the All, the All came forth from me and the All attained to me.  
Cleave a piece of wood, I am there; lift up the stone and you will find me there."


This is Full, That is Full. From the Full has come the Full.
The Full having come from the Full, that which remains yet is the Full.

See  Poornamadah for a more detailed explanation of the Poornamadah slokam.