Finding biographies of Arabic individuals can be a very complex process. The process differs greatly for modern vs pre-modern individuals. Please see the links below for detailed help.
The following bibliography is a helpful introduction to Arabic biographical dictionaries in that it lists many of the major dictionaries, at least up to 1987, and states their coverage.
Arabic biographical dictionaries : a summary guide and bibliography / by Paul Auchterlonie
Durham : Middle East Libraries Committee, 1987
iv, 60 p. ; 24 cm
(Research guides / Middle East Libraries Committee, 0269-0233 ; 2)
Medieval Arabic Biography