Private property is often defended by philosophers with an apeal to the "rights" of man. In both Hegel and Marx the concept of "rights" to private property can be understood within the dialectical conception of a contradiction.
Marx from The Critique of the Gotha Program:
It [private property] is, therefore, a right of inequality, in its content, like every right. Right, by its very nature, can consist only in the application of an equal standard; but unequal individuals (and they would not be different individuals if they were not unequal) are measurable only by an equal standard insofar as they are brought under an equal point of view, are taken from one definite side only -- for instance, in the present case, are regarded only as workers and nothing more is seen in them, everything else being ignored. Further, one worker is married, another is not; one has more children than another, and so on and so forth. Thus, with an equal performance of labor, and hence an equal in the social consumption fund, one will in fact receive more than another, one will be richer than another, and so on. To avoid all these defects, right, instead of being equal, would have to be unequal.[my emphasis]
Hegel from The Phenemomenology of Mind (Spirit):
Property therefore contradicts itself on all hands just as much as absence of property; each has within it both theses opposite and self contradictory moments, universality and particularity.
There were of course a number of major differences between Marx and Hegel on the meaning of private property.