"Great kindness; great mercy": Augustine on adoption

Augustine's second homily on the Gospel of John offers one of the richest commentaries on John 1.12 that I have read. His explanation of what it means for God to give us "the right to become children of God" is worth quoting in full:

What did he bestow on them? Great kindness; great mercy. Singly born, he did not wish to remain one and only. Many couples who have had no children adopt some when advanced in years and realize by choice what nature was unable to provide; that is what human beings do. But someone who has an only son rejoices in him all the more, because he alone will take possession of the whole inheritance and not have anyone else to divide it with and thus turn out the poorer. Not so God; he sent the very same one and only Son he had begotten, through whom he had created everything, into this world so that he should not be alone but should have adopted brothers and sisters. You see, we were not born of God in the same way as the only-begotten Son of his, but we were adopted through the Son's grace. For the only-begotten Son came to forgive sins, those sins which had us so tied up that they were an impediment to his adopting us; he forgave those he wished to make his brothers and sisters and made them co-heirs... No, he was not afraid of having co-heirs, because his inheritance is not whittled down if many possess it. They themselves, in fact, become the inheritance which he possesses, and he in turn becomes their inheritance (Homilies on the Gospel of John [New City Press, 2009], pp. 64-65).

The beauty of Augustine's description of adoption speaks for itself. A few observations are nevertheless worth making.

(1) Augustine's homily is a helpful reminder that faithful biblical exposition did not begin in the modern era. Patristic sermons and biblical commentaries will inevitably strike evangelicals as strange territory. Nonetheless, it is territory that repays patient exploration.  

(2) Much of the power of the doctrine of adoption lies in the disanalogy that obtains between human adoption and divine adoption. Human couples often adopt because they lack natural offspring. Human couples with an only child (at least in Augustine's day) often rejoice in the fact that their offspring can be the sole heir of their inheritance (and thus can avoid the poverty that might accompany dividing their inheritance). "Not so God": He sacrificed what he had--his eternally begotten, eternally beloved Son--to enrich his enemies by making them joint-heirs with Christ. 

(3) We cannot appreciate the full depths of the gospel apart from the doctrine of the Trinity. The doctrine of the Trinity teaches us about the kind of love that is on display in the gospel. The Father eternally loves the Son, and this love is the measure of what the gospel cost: the Father loved us by sacrificing his beloved Son to forgive those sins that "were an impediment to his adopting us." Moreover, the Father's love for the Son is the measure of what the gospel bought: the Father loved us by bequeathing to us an inexhaustible inheritance, which is nothing other than the right to become an heir of the Father's love in and with Jesus Christ, his beloved Son. Truly this is "great kindness; great mercy."