פירוש על קידושין 52:3

In this story a man wants to give away movables but the movables are not with him. So he buys a small plot of land, which here we seem to think cost a sela (very small amount of money for land). Clearly, a hundred sheep and a hundred barrels cannot fit on this piece of land. Nevertheless, by giving away the tiny piece of land land, he is also able to give away the sheep. This proves that the movables need not be on the land.