I don't think Groucho ever said anything about labor one way or the other.
Money.
The mind AKA; thinking, imagination and creativity, these are at the root of wealth creation. Muscles do not create wealth, thought does!
People investing capital in superior production methods to more efficiently make items of higher demand creates wealth.
Capital mobility facilitates this, it means people and money are free to move where they receive the most gain.
Marx never considers that the value of things depends on demand, so every object that takes the same amount of labor to make is equally valuable under marxism. Gee why didn't that work.
Source of wealth was supposed to be "added value" derived from pernicious exploitation. Labor was considered to be the primary source of this "added value" [as being the most convenient and plentiful to exploit], hence the "avant-gard of society" with all the rest of that crap thrown in there like the icing on a cake.
Google "Marx Labor Theory of Value."
Labor is ultimately the source of all wealth but undifferentiated labor is not the measure of the value af anything. Marx was wrong in that he thought that labor was indiscriminately quantifiable, i.s. an hour working a drill press on an assembly line has the same value as an hour on a shovel. Labor is the source of wealth. But some labor produces less wealth than other labor.