Labor Time Quotes

A use-value, or useful article, therefore, has value only because abstract human labour is objectified or materialized in it. How, then, is the magnitude of this value to be measured? By means of the quantity of the "value-forming substance", the labour, contained in the article. This quantity is measured by its duration, and the labour-time is itself measured on the particular scale of hours, days etc.

Karl Marx

What exclusively determines the magnitude of the value of any article is therefore the amount of labour socially necessary, or the labour-time socially necessary for its production.

Karl Marx

As exchange-values, all commodities are merely definite quantities of congealed labour-time.

Karl Marx