The Master and Pupil

Long time ago there was a man who had a very clever son. One-day the son went out from parent's home to seek a job. And on the way he met a man, who asked him where he was going.  He answered that he wants a job. The man took him into his service, and the entire boy's work was to dust his master's books. His master was a great wizard and could perform all kinds of magic. The boy had plenty of time to read all master's books. When he learned all books he thought that there is no need it to stay here any longer, so he returned his parents’ home again. What he wanted to do with new skills?