To serve God does not mean giving him any gift, nor has God any need of our service. On the contrary, it is he who gives to those who serve him life, immortality and eternal glory.
He rewards those who serve him without deriving any benefit himself from their service: he is rich, he is perfect, he has no needs.
God requests human obedience so that his love and his pity may have an opportunity of doing good to those who serve him diligently. The less God has need of anything, the more human beings need to be united with him.
Consequently, a human being’s true glory is to persevere in the service of God