Book Four, Chapter Two.
Not a surprise that PJB got it right, by the way...
Homework assignment, Rudeboy--you're still in grad school, right? OK. Disprove Smith. (Or Samuelson...)
"Disprove" Smith? I embrace him, especially the following from Book Four, Chapter Two (say, isn't that what you claim to have read?):
It is the maxim of every prudent master of a family never to attempt to make at home what it will cost him more to make than to buy. . . .
What is prudence in the conduct of every private family can scarce be folly in that of a great kingdom. If a foreign country can supply us with a commodity cheaper than we ourselves can make it, better buy it of them with some part of the produce of our own industry employed in a way in which we have some advantage.