Full Idea
Since that which is moved and which also moves is an intermediate, it follows that there must be something that moves without being moved.
Gist of Idea
Something which both moves and is moved is intermediate, so it follows that there must be an unmoved mover
Source
Aristotle (Metaphysics [c.324 BCE], 1072a19)
Book Reference
Aristotle: 'Metaphysics', ed/tr. Lawson-Tancred,Hugh [Penguin 1998], p.373