The answer is: materialism.
The fox tempts the young boy with not only comfort and perhaps the satisfaction of a bodily need, which could be protecting himself from the cold, but the fox adds the unnecessary temptation of material luxury in the guise of a fine fur. In colloquial terms, materialism refers to the value added to goods that are wasteful and that are not conducive to edification by imposing rough materiality on spiritual needs of a higher stance, represented in the text by the treasure that the boy is seeking.