In today’s Office of Readings, St Irenaeus speaks about the friendship of God.
Our Lord, the Word of God, first drew men to God as servants, but later he freed those made subject to him. He himself testified to this: I do not call you servants any longer, for a servant does not know what his master is doing. Instead I call you friends, since I have made known to you everything that I have learned from my Father. Friendship with God brings the gift of immortality to those who accept it.
Nor did the Lord need our service. He commanded us to follow him, but his was the gift of salvation. To follow the Saviour is to share in salvation; to follow the light is to enjoy the light. Those who are in the light do not illuminate the light but are themselves illuminated and enlightened by the light. They add nothing to the light; rather, they are beneficiaries, for they are enlightened by the light.
The same is true of service to God: it adds nothing to God, nor does God need the service of man. Rather, he gives life and immortality and eternal glory to those who follow and serve him. He confers a benefit on his servants in return for their service and on his followers in return for their loyalty, but he receives no benefit from them. He is rich, perfect and in need of nothing.