To close up any loose ends from the last post on Christ, The Mediator, Part 2 and also Christ, The Mediator, Part 1 (see Gal. 3:19-20; 1 Timothy 2:5; Heb. 8:6, 9:15, 12:24) the following excerpt is from a paper, “Reformed Baptist Covenant Theology and Biblical Theology” written by Micah and Samuel Renihan during their studies at Westminster Seminary California. You can read the paper in its entirety here: http://thelogcollege.files.wordpress.com/2012/11/rb-cov-theo-renihans.pdf
Jesus Christ has been and always will be the federal head of the Covenant of Grace/New Covenant. To be federally united to him you must be 1. promised to him outside of time in the Covenant of Redemption and 2. brought into union with him in time by the Holy Spirit.
The Son was the one elected by the Father to win the redemption of the elect. All of this is accomplished in the New Covenant, which is the historical climax of the Covenant of Grace. To be in the Covenant of Grace/New Covenant, you must be united to Christ, its federal head.15 Since the Covenant of Grace is the retro-active application of the New Covenant, if we posit that Christ is the mediator of the Covenant of Grace, we can only understand the terms of his role as mediator, and our relation to him as such, through the way that he is presented in the New Covenant. That Christ is the mediator of the Covenant of Grace, the New Covenant, no Reformed theologian denies. Thus, in line with New Testament doctrine, the only way to be under Christ’s federal headship is to be united to him by the Holy Spirit. This union finds its roots outside of time as we are chosen in Christ in the Covenant of Redemption and is applied to the elect in time by the Spirit, begun in effectual calling and consummated in the faith of the believer. Apart from saving faith there can be no union with Christ, because the Spirit does not indwell any except the elect, those who have been justified by faith.16 Christ is the one and only federal head of the Covenant of Grace, the New Covenant. Federal headship is never mediate, thus none can enter the Covenant other than those who are directly or immediately under his federal headship by the Holy Spirit.17
Vos says, “However narrowly or widely the boundary of the covenant of grace be drawn, in any case it involves a relationship with Christ, whether external or internal, by which it is tied to the covenant of redemption.”18
One is first united to Christ, the Mediator of the covenant, by a mystical union, which finds its conscious recognition in faith. By this union with Christ all that is in Christ is simultaneously given. Faith embraces all this too; it not only grasps the instantaneous justification, but lays hold of Christ as Prophet, Priest, and King, as his rich and full Messiah.19
On the Christian position there can be no doubt that all the benefits of grace have been completely and solely acquired by Christ; hence, they are included in his person and lie prepared for his church in him…And since these benefits are all covenant benefits, were acquired in the way of the covenant, and are distributed in the same covenantal way, there is no participation in those benefits except by communion with the person of Christ, who acquired and applies them as the mediator of the covenant.20
Here, precisely as in the rending of the veil for the ceremonials of Judaism, the exclusive bond for the people was broken at the center: Christ’s very mother and brothers were to have no precedence over others, nor any distinctive position in His kingdom; spiritual relations alone should prevail there, and the one bond of connection with it for all alike, was to be the believing reception of the gospel and obedience to it…So far, therefore, as regards Israel’s typical character, their removed and isolated position is plainly at an end: all tribes and nations are on a footing as to the kingdom of God – members and fellow-citizens if they are believers in Christ, aliens if they are not.21
Fairbairn adds, “And wherever there is found a soul linked in vital union with Christ, there also are found the essential characteristics of Abraham’s seed, and title to Abraham’s inheritance.”22
Rom. 8:9 “Anyone who does not have the Spirit of Christ does not belong to him.”
Rom. 10:11-13 “For the Scripture says, “Everyone who believes in him will not be put to shame.” 12 For there is no distinction between Jew and Greek; for the same Lord is Lord of all,23 bestowing his riches on all who call on him. 13 For “everyone who calls on the name of the Lord will be saved.””
1 Cor. 12:11-13 “All these are empowered by one and the same Spirit, who apportions to each one individually as he wills. 12 For just as the body is one and has many members, and all the members of the body, though many, are one body, so it is with Christ. 13 For in one Spirit we were all baptized into one body–Jews or Greeks, slaves or free–and all were made to drink of one Spirit.”
Gal. 3:26-28 “For in Christ Jesus you are all sons of God, through faith. 27 For as many of you as were baptized into Christ have put on Christ. 28 There is neither Jew nor Greek, there is neither slave nor free, there is no male and female, for you are all one in Christ Jesus.”
Eph. 1:22-23 “And he put all things under his feet and gave him as head over all things to the church, 23 which is his body, the fullness of him who fills all in all.”24
Eph. 4:4-6 “There is one body and one Spirit–just as you were called to the one hope that belongs to your call– 5 one Lord, one faith, one baptism, 6 one God and Father of all, who is over all and through all and in all.”
The Covenant of Grace is so called because its blessings are freely given to its members. Those blessings are free because they have been won solely by Christ’s obedience in fulfillment of his commission in the Covenant of Redemption. Thus understood, the Covenant of Grace arises in history in contradistinction to the Covenant of Works. That covenant having been broken, all mankind is born immediately federally united to Adam, under the curse of the law. When man is liberated from this condemnation, his liberation comes through the propitiatory satisfaction of Christ on his behalf and the gracious imputation of Christ’s righteousness to his account, appropriated by faith. In other words, as Genesis 3 shows, the Covenant of Grace is the solution to the curses of the Covenant of Works.
The fact that we see this redemption promised and typified from the fall onward has led reformed theologians to see God’s grace extending into history prior to the incarnation and death of Christ. Where God’s grace extended into the past, it came by way of covenant, wherein Christ’s blood of the New Covenant was retroactively applied to those who believed in the promise, and that retroactivity of the New Covenant was and remains distinct from the Old Covenant. Thus, Christ’s people have always been those who were promised to him by the Father, and it is those people for whom he spilled his blood.
Scripture teaches that Christ brings his own to himself through the work of the Spirit, and that he dwells in his own by the Spirit. Therefore, without the Spirit, none belong to Christ. If you belong to Christ, you are in the Covenant of Grace. If you do not belong to Christ, you are in the Covenant of Works. You cannot be in both.25 If it is possible to be born into the Covenant of Grace through the mediated federal headship of a parent, then, unless regeneration is presumed, one is both in Adam and in Christ at the same time. However, this is impossible. One man sinned and brought death to all mankind; another obeyed and brought life to his people. You are either in Adam or in Christ. 10
To bring this to a conclusion, a right understanding of the membership of the Covenant of Grace is founded on the Covenant of Redemption and the New Covenant. Those who are in the Covenant of Grace are those who were promised to the Son by the Father in the Covenant of Redemption, won by the Son’s life, death, and resurrection, and sealed by the Holy Spirit, uniting them to their federal head, Jesus Christ. Laying claim to Christ and his benefits is a serious matter, and as scripture shows, only those who have saving faith can truly make that claim. There is no external federal relation to Jesus Christ. In terms of membership or qualification, there are no distinctions in the body of Christ, that is, the church. All are sons of God through faith, under one head, indwelt by one Spirit. “Anyone who does not have the Spirit of Christ does not belong to him” (Rom. 8:9). In spite of the false professions, unbelief, and lies of apostates, God knows his own, Christ knows his sheep, and the Spirit of adoption knows the children of God.26 The covenant people of God are “a chosen race, a royal priesthood, a holy nation, a people for his own possession” (1Pet 2:9). The glorious New Covenant does not look to the Old for its pattern and people but stands on the eternal foundation of the Covenant of Redemption and comes to the elect as a Covenant of Grace, purchased, mediated, and eternally kept by “our great God and savior Jesus Christ who gave himself for us to redeem us from all lawlessness and to purify for himself a people” (Titus 2:14).
17 Cf. WLC 65-69.
18 Vos, 252.
19 Vos, 256.
20 Bavinck, 591, emphasis added.
21 Patrick Fairbairn, The Interpretation of Prophecy (London: The Banner of Truth, 1964), 261-62.
22 Fairbairn, 270.
23 All italics in Scripture verses are added for emphasis.
24 Cf. Eph. 5:23, Col. 1:18.
25 Cf. Rom. 7:4-6.