Adam Clarke on 2 Samuel 23:23

David set him over his guard - The Vulgate renders this, Fecitque eun sibi David auricularium a secreto, "David made him his privy counsellor;" or, according to the Hebrew, He put him to his ears, i.e., confided his secrets to him. Some think he made him a spy over the rest. It is supposed that the meaning of the fable which attributes to Midas very long ears, is, that this king carried the system of espionage to a great length; that he had a multitude of spies in different places.