Full Idea
I think it is a self-evident proposition that two bodies cannot be in the same place.
Gist of Idea
Obviously two bodies cannot be in the same place
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 4.07.05)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.594
A Reaction
If you accept this, and you want to define what a physical 'body' is, then clearly this condition must be implicitly or explicitly included.