The superintendants of the social and economic surplus in the biblical regime are the lower classes.
Every successful society eventually must face the challenge of how to digest the surpluses it produces. In the biblical regime the lower classes become the agents of integrating the surplus into the social fabric.
The surplus is the true engine and the funder of how society moves from stage to stage in its progress. The over-supply of resources in an economy functions as a leading indicator of crises looming in society. When a society undergoes successful social change it leads to the production of excess, and when the society has to figure out what to do with the excess it creates a social crisis.
By spending the surplus on the lower classes, the possibilities of improving the human capital of the country are enhanced while at the same time reducing the problem of a looming social crisis.
Spending the surplus on the lower classes also reduces the surplus and translates it into the institutions of society that serve as the basis of the next stage of the society. When a surplus is well digested by a society, social progress in that society goes smoothly.