Below is an excerpt from Chapter 30 of The Oxford Handbook of Reformed Theology , by Todd Billings. Dr. Billings is Gordon H. Girod Research Professor of Reformed Theology at Western Theological Seminary in Holland, Michigan. He is the author of several books, including Union with Christ, and The End of the Christian Life.

Classical Reformed Formulations of Union with Christ
The soteriology of union with Christ is ultimately grounded in the union of God himself with human flesh in the incarnation. As John’s prologue testifies, ‘the Word became flesh and made his dwelling among us’ (John 1:14). This incarnational union is sometimes spoken about as being ‘in Christ’ in relation to God: ‘God was in Christ reconciling the world to himself’ (2 Cor. 5:19). But most significantly, the union of God and humanity in Christ (the hypostatic union) is the indispensable theological doorway for making sense of the more common ‘in Christ’ language in the New Testament. Because Jesus Christ is the one in whom God and humanity commune perfectly, those who are adopted ‘in Christ’ can partake in this divine–human communion of God’s household. As Vermigli noted in a letter to Calvin, in order to understand the ‘mode of our union with Christ’, we first need to recognize the fundamental union of God with the human race in the incarnation, such that Jesus is our brother. Indeed, ‘the whole human race already has communion with Christ in this manner’. Yet, this ‘natural fellowship’ is not redemptive in itself, but enters us into a new communion generated by the Holy Spirit, who enables faith among the elect and brings the gifts of justification and new life in Christ (translation Garcia 2008: 274–6).
The vast majority, then, of ‘in Christ’ language in the New Testament refers to the Spirit-generated adoption of persons into union with Christ and into the covenant community of the church. There is both a vertical (God-directed) and a horizontal (other-directed) dimension, so to speak. For early Reformed exegetes, these two dimensions were closely interrelated and affirmed, yet most of the sixteenth- and seventeenth-century controversies revolved around the content of the vertical dimension. In late modern biblical scholarship, the exegesis has often focused more upon disputes regarding the content of the horizontal dimension. We will turn to each in due turn.
For classical Reformed theology, a key overall framework for speaking about the benefits of union with Christ in relation to God is succinctly expressed by John Calvin: ‘By partaking of him [Christ], we principally receive a double grace: namely, that being reconciled to God through Christ’s blamelessness, we may have in heaven instead of a Judge a gracious Father; and secondly, that sanctified by Christ’s spirit we may cultivate blamelessness and purity of life’ (Calvin 1960: 3:11:1). While received simultaneously, the first gift of this ‘double grace’ is justification—the forgiveness of sins, the free pardon of God based upon the righteousness of Jesus Christ. The second gift of the double grace is regeneration and sanctification—the new life generated by the Spirit resulting in works of love toward God and neighbor. Calvin insists that the two gifts must be distinguished—like the natures of Christ at Chalcedon, they are ‘without confusion’ and ‘without mixture’. A mixture between the two would both violate his biblical exegesis of the apostle Paul on justification and it would turn sanctification into a sham of self-righteousness: rather than obeying God in gratitude for the gratuitous gift of justification—as children serve a ‘gracious Father’—Christians would serve God and neighbour ultimately for their own sake, seeking merit through their good works. Instead, for Calvin, the Christian life is one of gratitude precisely because it is a response to God’s astonishing grace in justification.
Yet, while Calvin insisted that justification and sanctification remain distinct, avoiding the turning of the Christian life into moral calculus, he just as vigorously emphasized that sanctification is not an optional ‘extra’ for Christians. Indeed, it is not the case that justification is God’s work in Christ and sanctification is primarily human work. Both are gifts received in union with Christ—thus the gifts are ‘without division, without separation’ as Chalcedon declares about Christ’s two natures. This means that regenerate Christians always bear the fruit of good works, even though it is not through good works that salvation is either accomplished or received:
Do you wish, then, to attain righteousness in Christ? You must first possess Christ; but you cannot possess him without being made partaker in his sanctification, because he cannot be divided into pieces. Since, therefore, it is solely by expending himself that the Lord gives us these benefits to enjoy, he bestows both of them at the same time, the one never without the other. Thus it is clear how true it is that we are justified not without works yet not through works, since in our sharing in Christ, which justifies us, sanctification is just as much included as righteousness.
(Calvin 1960: 3:16:1)
In light of this formulation, it is not surprising that Calvin claims that the ‘sum of the Gospel’ is justification and sanctification received in union with Christ (Calvin 1960:
3:3:1). Calvin does not downplay the significance of justification by faith alone—indeed, Calvin insists that it is ‘the main hinge on which religion turns’. And yet, the Gospel always entails more than forgiveness alone or justification by faith alone. It involves no less than adoption as children of God, receiving a new status and new life through Christ by the Spirit.
As a second-generation codifier of the Reformed tradition, Calvin was not seeking to be unique; in his theology of union with Christ, he is characteristic of the broader Reformed tradition, particularly as expressed in the Reformed confessions. Although he is distinctive in the phrasing of the ‘double grace’, the notion that justification and sanctification are distinct yet inseparable gifts received in union with Christ by the Spirit is expressed in a wide range of Reformed confessions.
For example, consider the Belgic Confession of 1561, which reflects the influence of Calvin in quite clear ways and received the approval of Calvin by letter. It has three
articles on union with Christ and salvation: the first (article 22) introduces the role of faith and union with Christ, and then articles on justification (article 23) and sanctification follow (article 24). The Holy Spirit ‘kindles in our hearts a true faith that embraces Jesus Christ, with all his merits, and makes him its own, and no longer looks for anything apart from him’. Thus, this Spirit-enabled faith is ‘the instrument that keeps us in communion with him [Christ] and with all his benefits’. In article 23, justification is ‘the forgiveness of our sins because of Jesus Christ’ based not on ‘ourselves or our merits’ but ‘on the sole obedience of Christ crucified, which is ours when we believe in him’. Justification has a particular consequence, which points to its role in preceding sanctification, and thus purifying it from obeying God out of servile fear. Justification ‘free[s] the conscience from the fear, dread, and terror of God’s approach’. As the Belgic exposits sanctification, it insists that sanctification is distinct yet inseparable from justification, for ‘it is impossible for this holy faith to be unfruitful in a human being’ (Our Faith 2013: 46–9).
Other early Reformed confessions follow a roughly similar pattern, even if they do not as clearly mirror Calvin specifically. Confessions such as the Heidelberg Catechism
emerge from diverse theological sources—with a variety of influences such as Philippist Lutherans and Zurich theologians (especially Bullinger). Yet its doctrine of union with Christ is central to its soteriology. From its initial question and answer, it draws upon the substance of a shared confessional theology of union, justification, and sanctification. In its characteristic way, it gives the doctrine a pastoral emphasis: that ‘your only comfort in life and in death’ is that ‘I am not my own, but belong—body and soul, in life and in death—to my faithful Savior Jesus Christ’. This hope is grounded in the work of Christ who ‘fully paid for all my sins with his precious blood, and has set me free from the tyranny of the devil’. Christ’s work on the Cross is received by the Spirit in union with Christ, who empowers the believer for grateful service. ‘Because I belong to him, Christ, by his Holy Spirit, assures me of eternal life and makes me wholeheartedly willing and ready from now on to live for him’ (Our Faith 2013: 69).
Confessions, by their nature, do not tend to be sites of innovation. But on union with Christ, perhaps the most creative development in the early Reformed confessions comes in the Heidelberg Catechism, Q and A 31 and 32. As Ursinus makes clear in his commentary, he describes Christ’s person and work in the three offices and then moves to a direct parallel of a derivative, subordinate participation of Christians in the three offices through Christ. After explaining how Christ is called ‘anointed’ because he is our prophet, priest, and king, Q and A 32 describes the Spirit’s anointing of the Christian in terms of union with Christ, reflecting these three offices:
Q. But why are you called a Christian?
(Our Faith 2013: 80)
A. Because by faith I am a member of Christ and so I share in his anointing. I am anointed to confess his name, to present myself to him as a living sacrifice of thanks, to strive with a free conscience against sin and the devil in this life, and afterward to reign with Christ over all creation for eternity.
This strong account of union (‘I am a member of Christ’) by the Spirit (sharing in Christ’s ‘anointing’) leads to a threefold aspect of Christian identity: through faith, Christians are ‘engrafted into Christ as members to the head, that we may be continuously sustained, governed and quickened by him; and because he makes us prophets, priests and kings unto God and his Father, by making us partakers of his anointing’. This new identity conferred upon Christians is an ‘unspeakable dignity’ and it calls forth a response in action. For in this new, anointed identity is ‘a participation in all of the gifts of Christ’ including the three offices. This participation is subordinate and derivative. As prophets, Christians declare someone other than themselves—they ‘confess his name’, and, in Ursinus’ commentary, teach ‘the true doctrine of God necessary for salvation’. As priests, Christians depend upon the full priesthood of Christ as they pray and intercede for others, offer alms to those in need, and gratitude to God. ‘Christ offered up a sacrifice of thanksgiving and propitiation, at the same time, we offer only sacrifices of thanksgiving.’ As kings, believers participate in Christ’s kingship in striving ‘against sin and the devil in this life’, looking forward to a kingdom when we ‘reign with Christ over all creation for eternity’. And yet the logic of union is once again combined with that of subordination and derivation: ‘Christ conquers his enemies by his own power, but we overcome our foes in and through him’ (Ursinus 1954: 179–80).
From The Oxford Handbook of Reformed Theology edited by Michael Allen and Scott R. Swain. Copyright © 2020 by Michael Allen and Scott R. Swain and published by Oxford University Press. All rights reserved.