Marx: No admittance except on business

Accompanied by Mr. Moneybags and by the possessor of labour-power, we therefore take leave for a time of this noisy sphere, where everything takes place on the surface and in view of all men, and follow them both into the hidden abode of production, on whose threshold there stares us in the face "No admittance except on business." Here we shall see, not only how capital produces, but how capital is produced. We shall at last force the secret of profit making. This sphere that we are deserting, within whose boundaries the sale and purchase of labour-power goes, is in fact a very Eden of the innate rights of man. There alone rule Freedom, Equality, Property and Bentham.

Capital, Vol. 1 p195 1915 edition (Google Books)