The greater part of this intricate yet unified system of government is carried on by unpaid work. Elected deputies, whether to village or the All-Union Congress, receive no salaries of office. They draw their usual wages from the factory or institution which sends them and in which they keep on working, except insofar as they may be “released from production” for the needs of government; this varies with the importance of the work they do. There is thus no hard and fast line between the citizen and the man in office. Deputies are a link between the collective life of the factory and the larger collective life of the country. Any worker may approach them conveniently any day in their place of work to ask about the fulfillment of instructions given by the voters. They may be recalled by their constituents at any time simply through a factory meeting.

(emphasis mine)

This seems to counter those ultra leftists (eg Trotskyists), who accuse the Soviet Union of "state capitalism" and of having a political / bureaucratic "class", that's fundamentally materially different from the workers.