Salam sorry please forgive me, i don't know maybe a misunderstanding but Asaf isn't a prophet per say, he was just a man sent by Allah to Soloman (i believe) with apart of the book of knowledge to help Solomen and to stop him from using the Jinns as they can do harm to him as well (i believe)...im still looking for some authentic sites, but the ayat that talks about it, i think u should (and maybe I should) re-read the whole surah to get the real deal...unless u have done some research...mind sharing?