The Wealth of Nations by Part 2 Chapter 2 Page 10

that of the society to which he belongs, it is not upon that account totally excluded from making a part likewise of their net revenue. Though the whole goods in a merchant’s shop must by no means be placed in his own stock reserved for immediate consumption, they may in that of other people, who, from a revenue derived from other funds, may regularly replace their value to him, together with its profits, without occasioning any diminution either of his capital or of theirs.

Money, therefore, is the only part of the circulating capital of a society, of which the maintenance can occasion any diminution in their net revenue.

The fixed capital, and that part of the circulating capital which consists in money, so far as they affect the revenue of the society, bear a very great resemblance to one another.