The person who puts to death by the Spirit the deeds of our sinful nature will live, says the Apostle. This is not surprising since one who has the Spirit of God becomes a child of God. So true is it that he is a child of God that he receives not a spirit that enslaves but the Spirit that makes us sons. So much so that the Holy Spirit bears witness to our spirit that we are sons of God. This is the witness of the Holy Spirit: he cries out in our hearts, Abba, Father, as we read in the letter to the Galatians.
There is also that other great testimony to the fact that we are sons of God: we are heirs of God, co-heirs with Christ. A co-heir of Christ is one who is glorified along with Christ. The one who is glorified along with him is one who, by suffering for him, suffers along with him.
To encourage us in suffering, Paul adds that all our sufferings are small in comparison with the wonderful reward that will be revealed in us; our labours do not deserve the blessings that are to come. We shall be restored to the likeness of God, and counted worthy of seeing him face to face.
He enhances the greatness of the revelation that is to come by adding that creation also looks forward to this revealing of the sons of God. Creation, he says, is at present condemned to frustration, not of its own choice, but it lives in hope. Its hope is in Christ, as it awaits the grace of his ministry; or it hopes that it will share in the glorious freedom of the sons of God and be freed from its bondage to corruption, so that there will be one freedom, shared by creation and by the sons of God when their glory will be revealed.
At present, however, while this revealing is delayed, all creation groans as it looks forward to the glory of adoption and redemption; it is already in labour with that spirit of salvation, and is anxious to be freed from its subjection to frustration.
The meaning is clear: those who have the first fruits of the Spirit are groaning in the expectation of the adoption of sons. This adoption of sons is that of the whole body of creation, when it will be as it were a son of God and see the divine, eternal goodness face to face. The adoption of sons is present in the Church of the Lord when the Spirit calls out: Abba, Father, as you read in the letter to the Galatians. But it will be perfect when all who are worthy of seeing the face of God rise in incorruption, in honour and in glory. Then our humanity will know that it has been truly redeemed. So Paul glories in saying: We are saved by hope. Hope saves, just as faith does, for of faith it is said: Your faith has saved you.
This excerpt from a letter of St. Ambrose (Ep. 35, 4-6. 13; PL 16 [ed. 1845], 1078-1079, 10 81) comments on Paul’s Letter to the Galatians and its statement that we are heirs of God, coheirs with Christ, no longer subject to the Law but led by the Holy Spirit. It is used in the Roman Office of Readings on Wednesday of the 5th week in ordinary time with the accompanying biblical reading being Galatians 3:15-4:7.