The patristic writers all the way up through the Reformers were fond of stating the gospel in terms of participation and sharing. Athanasius’ wording perhaps is the most famous: God became man that man might become God. That is not to say that men become gods; rather, through salvation, mankind is thereby enabled share in God’s own life. Calvin and Luther had gospel formulations akin to this as well. For instance, Calvin, in his section on the Lord’s Supper in the Institutes, says this: becoming Son of man with us, he has made us sons of God with him.
The point here is that Jesus becomes what we are that we might become what he is. Or put another way, salvation is all about sharing. God shares in our humanity, in our suffering, in the consequences of our sins, that we might share in his infinitude and righteousness.
Kallistos Ware, in his The Orthodox Way, explains it this way:
The Christian message of salvation can best be summed up in terms of sharing, of solidarity and identification. The notion of sharing is a key alike to the doctrine of God in Trinity and to the doctrine of God made man. The doctrine of the Trinity affirms that, just as man is authentically personal only when he shares with others, so God is not a single person dwelling alone, but three persons who share each other’s life in perfect love. The incarnation equally is a doctrine of sharing or participation. Christ shares to the full in what we are, and so he makes it possible for us to share in what he is, in his divine life and glory. He became what we are, so as to make us what he is.
St Paul expresses this metaphorically in terms of wealth and poverty: “You know the grace of our Lord Jesus Christ: he was rich, yet for your sake he became poor, so that through his poverty you might become rich” (2 Cor 8:9). Christ’s riches are his eternal glory; Christ’s poverty is his complete self-identification with our fallen human condition. In the words of an Orthodox Christmas hymn, “Sharing wholly in our poverty, thou hast made divine our earthly nature through thy union with it and participation in it”. Christ shares in our death, and we share in his life; he “empties himself” and we are “exalted” (Phil 2:5-9). God’s descent makes possible man’s ascent. St Maximus the Confessor writes: “Ineffably the infinity limits itself, while the finite is expanded to the measure of the infinite”…
Christ who is the Son of God by nature has made us sons of God by grace. In him we are “adopted” by God the Father, becoming sons-in-the-Son. (p 73-74)