Is it permissible to buy and sell cats and dogs? Is raising them a sign of foolishness? And is it correct to describe Abu Hurairah as foolish because he used to raise a cat?

Selling and buying cats is impermissible, but raising them is permissible. Selling and buying dogs is impermissible, except for hunting dogs and guard dogs (which is a matter of differing opinion), and raising them is not permissible except for livestock dogs, hunting dogs, or farm dogs.