Of course there was a Book of Esther before this, and even in its redacted form our Esther reflects the period of three Persian kings, viz.
12-13 is indubitably a Pauline fragment, and the problem for the critic is to determine whether in the epistle as a whole we have a redacted and interpolated edition of what was originally a note from the hand of Paul, or whether the epistle drew upon some Pauline tradition '(connecting Titus with Crete) and material, and was afterwards interpolated at i.
In short, however imperfectly the Koran may have been redacted, in the majority of cases the present suras are identical with the originals.
The above works, although of 5th century or later date in their present form, contain much older material, which was perhaps first redacted in the earlier part of the 2nd century, A.D.
The last reference to him, as living, is in 1208, when an order for payment to him is on record, but Giraldus Cambrensis, in the second edition of his Hibernica, redacted in 1210, utters a prayer for his soul, "cujus animae propitietur Deus," a proof that he was no longer alive.