Full Idea
Of things there are, some are said of a subject, but are not in any subject. For example, man is said of a subject, the individual man, but is not in any subject.
Gist of Idea
Some things said 'of' a subject are not 'in' the subject
Source
Aristotle (Categories [c.331 BCE], 01a20)
Book Reference
Aristotle: 'Categories and De Interpretatione', ed/tr. Ackrill,J.R. [OUP 1963], p.4
A Reaction
See? 'Being a man' is not a property of a man! Only the properties which are 'in' the man are properties of the man. The rest are things which are said 'of' men, usually as classifications. A classification is not a property.