abort(403);
//You may also provide the exception's message and custom
//HTTP response headers that should be sent to the browser:
abort(403, 'Unauthorized.', $headers);
abort_if()
//The abort_if function throws an HTTP exception if a given
//boolean expression evaluates to true:
abort_if(! Auth::user()->isAdmin(), 403);

abort(404); - it will return to not found page.
Status Code	Meaning
404	Not Found (page or other resource doesn’t exist)
401	Not authorized (not logged in)
403	Logged in but access to requested area is forbidden
400	Bad request (something wrong with URL or parameters)
422	Unprocessable Entity (validation failed)
500	General server error