The Wealth of Nations by Part 4 Chapter 3 Page 66

The wealth of a neighbouring nation, however, though dangerous in war and politics, is certainly advantageous in trade. In a state of hostility it may enable our enemies to maintain fleets and armies superior to our own; but in a state of peace and commerce it must likewise enable them to exchange with us to a greater value, and to afford a better market, either for the immediate produce of our own industry, or for whatever is purchased with that produce. As a rich man is likely to be a better customer to the industrious people in his neighbourhood than a poor, so is likewise a rich nation. A rich man, indeed, who is himself a manufacturer, is a very dangerous neighbour to all those who deal in the same way. All the rest of the neighbourhood, however, by far the greatest number, profit by the good market which his expense affords them.