James S. Stewart wrote that “union with Christ, rather than justification or election or eschatology, or indeed any of the other great apostolic themes, is the real clue to an understanding of Paul’s thought and experience” (A Man in Christ [Harper & Bros., 1955], vii).
John Calvin said that union with Christ has “the highest degree of importance” if we are to understand justification correctly (Institutes 1:737).
John Murray wrote that “union with Christ is . . . the central truth of the whole doctrine of salvation. . . . It is not simply a phase of the application of redemption; it underlies every aspect of redemption” (Redemption—Accomplished and Applied [Eerdmans, 1955], pp. 201, 205).
Lewis Smedes said that it was “at once the center and circumference of authentic human existence” (Union with Christ [Eerdmans, 1983], xii).
Anthony Hoekema wrote that “Once you have your eyes opened to this concept of union with Christ, you will find it almost everywhere in the New Testament” (Saved by Grace[Eerdmans, 1989], 64.
Hoekema explains that the New Testament uses two interchangeable expressions to describe union with Christ:
- We are in Christ (2 Cor. 5:17; John 15:4, 5, 7; 1 Cor. 15:22; 2 Cor. 12:2; Gal. 3:28; Eph. 1:4, 2:10; Phil. 3:9; 1 Thess. 4:16; 1 John 4:13).
- Christ is in us (Gal. 2:20; Col. 1:27; Rom. 8:10; 2 Cor. 13:5; Eph. 3:17).
Hoekema says that we should see union with Christ “extending all the way from eternity to eternity.” He outlines his material in this way:
- The roots of union with Christ are in divine election (Eph. 1:3-4).
- The basis of union with Christ is the redemptive work of Christ.
- The actual union with Christ is established with God’s people in time.
Under the third point, he shows eight ways that salvation, from beginning to end, is in Christ:
- We are initially united with Christ in regeneration (Eph. 2:4-5, 10)
- We appropriate and continue to live out of this union through faith (Gal. 2:20; Eph. 3:16-17).
- We are justified in union with Christ (1 Cor. 1:30; 2 Cor. 5:21; Phil. 3:8-9).
- We are sanctified through union with Christ (1 Cor. 1:30; John 15:4-5; Eph. 4:16; 2 Cor. 5:17).
- We persevere in the life of faith in union with Christ (John 10:27-28; Rom. 8:38-39).
- We are even said to die in Christ (Rom. 14:8; 1 Thess. 4:16; Rev. 14:13).
- We shall be raised with Christ (Col. 3:1; 1 Cor. 15:22).
- We shall be eternally glorified with Christ (Col. 3:4; 1 Thess. 4:16-17).
And here’s a helpful quote from Sinclair Ferguson (in Christian Spirituality: Five Views of Sanctification [IVP, 1989], 58), explaining in a nutshell why union with Christ is the foundation for sanctification:
If we are united to Christ, then we are united to him at all points of his activity on our behalf.
- in his death (we were baptized into his death),
- in his resurrection (we are resurrected with Christ),
- in his ascension (we have been raised with him),
- in his heavenly session (we sit with him in heavenly places, so that our life is hidden with Christ in God), and we will share
- in his promised return (when Christ, who is our life, appears, we also will appear with him in glory) (Rom. 6:14; Col. 2:11-12; 3:1-3).
This, then, is the foundation of sanctification in Reformed theology.
It is rooted, not in humanity and their achievement of holiness or sanctification, but in what God has done in Christ, and for us in union with him. Rather than view Christians first and foremost in the microcosmic context of their own progress, the Reformed doctrine first of all sets them in the macrocosm of God’s activity in redemptive history. It is seeing oneself in this context that enables the individual Christian to grow in true holiness.
Some newer treatments of this important subject:
Robert Letham, Union with Christ: In Scripture, History, and Theology
Marcus Peter Johnson, One with Christ: An Evangelical Theology of Salvation
Elyse M. Fitzpatrick, Found in Him: The Joy of the Incarnation and Our Union with Christ
Robert Peterson, Salvation Applied by the Spirit: Union with Christ (forthcoming, 2014)