Marx:
In a higher phase of communist society, after the enslaving subordination of the individual to the division of labor, and therewith also the antithesis between mental and physical labor, has vanished; after labor has become not only a means of life but life's prime want; after the productive forces have also increased with the all-around development of the individual, and all the springs of co-operative wealth flow more abundantly—only then can the narrow horizon of bourgeois right be crossed in its entirety and society inscribe on its banners: From each according to his ability, to each according to his needs!
Just to be clear, I am talking about a fantasy world where all man’s needs are provided with little or no cost or effort. In the real world, work must be done to obtain these things and socialism leads to the exploitation of the industrious, by the lazy.
Also, even in a fanstasy world, where all needs are met, the fallen nature of man, would probably lead to arguments, fight and wars about how to allocate the excessive abundance. It is in man’s fallen nature to always think he is being shortchanged and deserves more and should work less. That is another reason (besides the running out of other people’s money problem) why socialism does not work.