TL;DR: The amount of free time that workers have and the way that they make use of it are very important indices of the population's standard of living as discussed by the authors, and this increased free time for the workers is one of the most important laws of socialism, which becomes increasingly evident to the extent that socialist society develops towards communism.
Abstract: The amount of free time that workers have and the way that they make use of it are very important indices of the population's standard of living. In a socialist society increased labor productivity permits a reduction in the work day, and this increased free time for the workers is one of the most important laws of socialism, which becomes increasingly evident to the extent that socialist society develops towards communism. This free time, in turn, and the concomitant fully-rounded development of the individual, are powerful factors in raising labor productivity.
TL;DR: A rapid rise in production and a steady increase in labor productivity in all branches of the national economy lead inevitably, in a socialist society, to reduction of the working day and an increase in the free time available to the working people.
Abstract: A rapid rise in production and a steady increase in labor productivity in all branches of the national economy lead inevitably, in a socialist society, to reduction of the working day and an increase in the free time available to the working people. This is one of the laws of the gradual transition to the higher phase of communism in which, as Marx put it, "the measure of wealth will no longer be working time but free time" ("From the Unpublished Manuscripts of Karl Marx," Bol'shevik, 1939, No. 11-12, p. 64).