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.', $headers);
abort_if()
//The abort_if function throws an HTTP exception if a given
//boolean expression evaluates to true:
abort_if(! Auth::user()->isAdmin(), 403);
php artisan vendor:publish --tag=laravel-errors
update the error page file according to the code
@section('message', __($exception->getMessage() ?: 'Server Error'))