Where in MLB rules does it say batting gloves are legal?

If they are legal for batters, then can a pitcher wear a glove on his pitching hand? If the reason for allowing batting gloves is to 'increase the quality of the grip on the bat' then it makes sense for a pitching glove to 'increase the quality of grip on the ball'. I'm sure a batter would agree, because very few batters look forward to an errant cold weather or drizzeld rain, 100 mph baseball heading straight for his . . . . assorted body parts.