Esther and the Canon

In Megillah 7a, Shmuel voices his view that scrolls of Esther do not render the hands impure because it was divinely inspired to be said but not necessarily to be written. However, throughout the tractate, Shmuel can be found expounding on verses from Esther (e.g. 11a, 13a). So, according to Shmuel himself, which is it? Was the book of Esther a sacred part of the Bible or not?

See here for an answer.