What is the ruling on a husband fondling his wife's anus by kissing it, licking it, and inserting a finger into it?

Each spouse may enjoy the other's body, except for what the Sharia prohibits, such as anal intercourse with the wife or during menstruation and postpartum bleeding. It is not permissible to insert a finger into the anus to touch impurities without need, and this may lead to anal intercourse, which is a major sin. The mentioned licking, if it involves touching impurities, is forbidden, and if it does not involve them, it is something that sound natures would reject.