Full Idea
Abelard argued from the commonly accepted definition of a universal as 'what can be predicated of man', that no external thing can ever be predicated of anything.
Gist of Idea
Nothing external can truly be predicated of an object
Source
report of Peter Abelard (works [1135]) by Claude Panaccio - Medieval Problem of Universals 'Peter'
Book Reference
'Routledge Companion to Metaphysics', ed/tr. Le Poidevin/Simons etc [Routledge 2012], p.50
A Reaction
It sounds to me as if Abelard is confusing predicates with properties! Maybe no external can be a property of anything, but I take predicates to just be part of what you can say about anything, and that had better included external facts.