Locke argued, in his Second Treatise on Civil Government, that an individual creates property by virtue of their labor. In other words, a piece of land becomes one's property when they work on it, or improve it. Because all land was originally given to all people in common by God, a person who creates property through their labor has a natural right to retain it. It is the purpose of government to protect this right, and not to take it away without the consent of its owner.
Marx and Engels commented on this line of thinking in Section II of the Communist Manifesto:
We Communists have been reproached with the desire of abolishing the right of personally acquiring property as the fruit of a man’s own labour, which property is alleged to be the groundwork of all personal freedom, activity and independence...
Marx and Engels argued that it was not the communists, but rather the bourgeoisie that had destroyed small property in the forms of small freehold farms:
Do you mean the property of petty artisan and of the small peasant, a form of property that preceded the bourgeois form? There is no need to abolish that; the development of industry has to a great extent already destroyed it, and is still destroying it daily.
They then argued that wage labor did not create property for the worker under a capitalist system, but in fact created capital, which was defined as "that kind of property which exploits wage-labor." The bourgeoisie, in short, had destroyed the kind of property that Locke had argued belonged to people by natural right, and then had the nerve to claim that attempts to redress this were a violation of those same natural rights. Marx and Engels did not proceed into a full critique of this theory of property, as Marx would later in Kapital, but they laid the framework for a thorough critique of the intellectual foundations of liberal capitalism.