$user = User::findOrFail($id);

if ($user->exists)
{
    $user::$rules['password'] = (Input::get('password')) ? 'required|confirmed' : '';
    $user::$rules['password_confirmation'] = (Input::get('password')) ? 'required' : '';
}

if ($user->updateUniques())
{
    Session::flash('successes', array_merge((array) Session::get('successes'), ['Pomyślnie zmieniono użytkownika']));
    return Redirect::route('users.show', ['users'   =>  $user->id]);
}

return Redirect::route('users.edit', ['users'   =>  $user->id])
    ->withErrors($user->errors())
    ->withInput(Input::except('password'));