What is a Christian testimony? If you ask many believers to give their testimonies, they will tell you about their experiences regarding how they became Christians. Some tell how troubled their lives were, how they were addicted to drugs, how they were in prison, how they were destitute, how their marriages were falling apart, or how God rescued them from other personal disasters. Some people who grew up in Christian homes are embarrassed by such testimonies because they never knew a time when they did not trust in and love Christ. I even know of one case in which a teenager made up a dramatic testimony because he thought that the absence of such an experience meant that something was wrong with his faith. Yet, the Spirit’s work in the soul is like the wind: “The wind blows where it wishes, and you hear its sound, but you do not know where it comes from or where it goes. So it is with everyone who is born of the Spirit” (John 3:8). Regardless of how we came to Christ, the only thing that matters is that we are born of the Spirit and that we are in Christ.

While all Christians have different experiences, in actuality, we all have the same testimony. Paul wrote, “For what we proclaim is not ourselves, but Jesus Christ as Lord, with ourselves as your servants for Jesus’ sake” (2 Cor. 4:5). Our experiences differ widely, but our testimony to the Savior should be the same. However, whether their experiences are dramatic or mundane, many professing Christians can say little about who Jesus is. Yet, unless we know who He is, we cannot understand what He does. Questions 36–40 in the Westminster Larger Catechism establish the identity of the Mediator of the covenant of grace as the God-man, Jesus Christ, who alone can save His people from their sins. Before all else, to testify to Christ, we need to know who He is and why He needed to be God and man in one person in order to save us.

The Mediator of the Covenant of Grace Is God the Son

The only Mediator of the covenant of grace is the Lord Jesus Christ, who, being the eternal Son of God, of one substance and equal with the Father, in the fullness of time became man, and so was and continues to be God and man, in two entire distinct natures, and one person forever (WLC 36).

Some say that they cannot make it a day without Jesus in their lives. Yet does this say enough? Who is Jesus? We must know Him: “For there is one God, and there is one mediator between God and men, the man Christ Jesus, who gave himself as a ransom for all, which is the testimony given at the proper time” (1 Tim. 2:5–6).

The catechism tells us three fundamental things about who Jesus is. First, He is “the eternal Son of God, of one substance and equal with the Father” (WLC 36; see John 10:30; Phil. 2:6). He is the Word who was with God and who was God (Isa. 9:6; John 1:1). He has divine names (Isa. 9:6; Rom. 9:5; 1 John 5:20). He has divine attributes, including knowing what is in man (John 2:25) and being present with His people to the end of the world (Matt. 28:20). He does divine works, such as creating the world (John 1:3; Col. 1:16) and sustaining it (Heb. 1:3). He accepted divine worship (Matt. 14:33; 29:17; John 9:38; Rev. 5:8–14).1 In short, Jesus is the second person in the Trinity, equal with the Father and the Spirit. His fundamental identity is the person of the Son of God.

Second, “in the fullness of time,” the eternal Son of God became man (John 1:14; Gal. 4:4; 1 Tim. 3:16). He came at the time God appointed, which was the right time in God’s plan. Just as He has every divine attribute, so Jesus has every human attribute. He was born, He lived, He trusted and obeyed God, He was hungry and thirsty, He rejoiced, He grieved, He suffered, and He died. He took on “the likeness of sinful flesh” (Rom. 8:3) and He was tempted in all things as we are, “yet without sin” (Heb. 4:15). Some say that to err is human, but is it really? Because Jesus had no sin, He was more human than we are. His humanity was humanity as God designed it to be.

Regardless of how we came to Christ, the only thing that matters is that we are born of the Spirit and that we are in Christ.

Third, Jesus is God and man “in two entire and distinct natures, and one person, forever” (WLC 36; see Heb. 7:24–25). Jesus is a divine person, not a human person. The second person of the Trinity became a human being, but He did not become a human person. The humanity of Christ is the humanity of the Son of God, the human nature being united to the divine in one person. Christ’s two natures do not mix to create one person. The person of the Son became man and the man Christ Jesus ever lives to make intercession for His people (v. 25). Jesus remained the form of God while He took on the form of a servant, so that all should confess that Jesus is Lord, to the glory of God the Father (Phil. 2:5–11).

Do we testify that Jesus is the Christ, the Son of the living God (Matt. 16:16)? Do we confess that He is God the Son come in the flesh?

How Did the Mediator of the Covenant of Grace Become Man?

Christ the Son of God became man, by taking to himself a true body, and a reasonable soul, being conceived by the power of the Holy Ghost in the womb of the virgin Mary, of her substance, and born of her, yet without sin (WLC 37).

How did the Son of God become man? He did not do so by subtracting from His divine nature, but by adding a human nature. He took “to himself a true body and a reasonable soul” (Westminster Shorter Catechism 22; see Heb. 2:14–17). He did not pretend to take a human body. Nor did He take a human body without a human soul. Just as the separation of body and spirit constitutes human death (James 2:26), so Jesus gave up His spirit when He died (John 19:30). His divine nature did not replace His human soul. He took on true human nature, including everything that it meant for Him to be human.

Jesus was also “conceived by the power of the Holy Ghost” (WSC 22; see Luke 1:27, 31, 35; Gal. 4:4). While He had no human father, the Spirit conceived Him “in the womb of the Virgin Mary.” He was born “of her substance,” just as every human baby is nurtured in the womb and born of the substance of its mother (Westminster Confession of Faith 8.2). Yet since He was the Son of God, Mary became the mother of God because she bore God in human flesh. We should not worship Mary or pray to her. Instead, we should believe in her Son like she did (Luke 1:47). Jesus became the Seed of the Woman (Gen. 3:15) without inheriting Adam’s original sin. Again, He was truly like us in every way, “yet without sin” (Rom. 8:3; Heb. 4:15).

Do you testify to Jesus as a true historical human person? “By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in the flesh is from God, and every spirit that does not confess Jesus is not from God” (1 John 4:2–3).

Why Did the Mediator of the Covenant of Grace Have to Be God?

It was requisite that the Mediator should be God, that he might sustain and keep the human nature from sinking under the infinite wrath of God, and the power of death; give worth and efficacy to his sufferings, obedience, and intercession; and to satisfy God’s justice, procure his favor, purchase a peculiar people, give his Spirit to them, conquer all their enemies, and bring them to everlasting salvation (WLC 38).

It is one thing to know who Jesus is. It is another thing to know why He has to be who He is in order to save us. The catechism gives three reasons why He had to be God.

First, His divine nature sustained and kept “his human nature from sinking under God’s wrath and the power of death.” The eternal Son is an infinitely glorious person. God’s wrath is equally infinite and eternal. Mere human beings cannot bear the infinite wrath of God, which is why hell is eternal for them. While Christ suffered in His human nature, the divine nature sustained Him in His sufferings. This was why “Christ also suffered once for sins, the righteous for the unrighteous, that he might bring us to God, being put to death in the flesh but made alive in the Spirit” (1 Peter 3:18). Peter also argued that it was impossible for death to hold Him (Acts 2:24–25). While a sinful man could die and not rise, death could not hold the righteous God-man when He died.

Second, Christ’s deity gave “worth and efficacy to his obedience, sufferings, and intercession” (WLC 38). God is not under the law, and He is not subject to obeying the law. The law reflects God’s character and will. Yet God sent His Son to be born of a woman so that He might be born under the law (Gal. 4:4) and to obey it to the point of death (Phil. 2:8). Scripture asks us, if a man sins against God, then who can intercede for Him (1 Sam. 2:25)? Yet, the eternal Son alone measures up to the character and matches the worth and glory of His Father. As the second Adam, Christ by His obedience made many righteous (Rom. 5:19). The blood He shed was the blood of God (Acts 20:28) because His humanity was the humanity of the Son of God. As man He prays for His people (John 17), but as the God-man He always prays according to His Father’s will and His intercession is always effective.

Jesus took on true human nature, including everything that it meant for Him to be human.

Third, His deity secures our salvation. The catechism lists many blessings flowing to us from Christ’s divinity: He could “satisfy God’s justice, procure his favor, purchase a peculiar people, give his Spirit to them, conquer all their enemies, and bring them to everlasting salvation” (WLC 38). He could satisfy divine justice because of He was equal to the task. He could purchase an entire people (Titus 2:13–14), while no mere man can redeem even his own soul (Ps. 49:7–8). As God, He can give the Spirit (Acts 2:33), while men can only receive the Spirit (Acts 2:38). He reigns until He puts all His and our enemies under His feet (1 Cor. 15:25) so that He might save us from our enemies (Luke 1:71). He is the author of everlasting salvation to all who obey Him (Heb. 5:9).

Why Did the Mediator of the Covenant of Grace Have to Be Man?

It was requisite that the Mediator should be man, that he might advance our nature, perform obedience to the law, suffer and make intercession in our nature, have a fellow feeling of our infirmities; that we might receive the adoption as sons, and have comfort and access with boldness unto the throne of grace (WLC 39).

If all of the above is true, then why did Jesus need to be man? The answer is that we must have a second Adam to undo the ruin brought by the first Adam (Rom. 5:12–21). We need a new representative before God to act in our place where our first representative failed. He advances our human nature, not only from the ruin of sin to restoration by grace. He makes us what we should have been, and even greater than what we would have been, if creation was never marred by sin. Christ makes us “partakers of the divine nature” (2 Peter 1:4) by restoring God’s image in us, and by bringing us closer to God in union with Christ than if Adam had never sinned. He did this through His human obedience (Rom. 5:19; Gal. 4:4; Phil. 2:8) and by His suffering and intercession for us “in our nature” (Heb. 2:14; 7:24–25). He sympathizes with us in our infirmities, and He helps us in our time of need when we come boldly to the throne of grace (Heb. 4:15–16). The Spirit of Christ, the eternal Son, brings us into God’s family as adopted sons.

Why Did the Mediator of the Covenant of Grace Have to Be God and Man in One Person?

The catechism concludes this section by saying, “It was requisite that the Mediator, who was to reconcile God and man, should himself be both God and man, and this in one person, that the proper works of each nature might be accepted of God for us, and relied on by us, as the works of the whole person” (WLC 40). Jesus’ divine nature united, inseparably and without mixture or confusion, to His true humanity meant that He could represent both parties in the covenant of grace. He represents the offended God, whose wrath looms over sinners. He represents offending man, who needs to be reconciled to God and God to Him. God is well pleased in His beloved Son (Matt. 3:17) and He is well pleased when we take pleasure in the Son and receive Him by faith. We must rely on the proper works of each nature as the God-man did them in our place. Christ was born of the Spirit so that we might be born of the Spirit. Christ obeyed God so that we might be counted righteous. Christ suffered so that we should escape the wrath of God, in this life and in the next. Christ rose so that we might live in Him—both in this life and the next. Christ ascended into heaven so that we might have a place there. Christ will come again to receive us to Himself. Christ’s works as the God-man must be “relied on by us” because God accepts them “for us.”

The Spirit of Christ, the eternal Son, brings us into God’s family as adopted sons.

Jesus is the unique person to whom all Christians testify. I know a man who was an alcoholic. He wrecked his marriage. He lost his job, and he alienated his friends and family. He became destitute. Then a twelve-step program radically transformed his life. He remarried and has a strong marriage. He has a good job. He reconciled with his family and others. He became a spiritual man. The problem is that he does not know the Mediator of the covenant of grace. Jesus asked, “What does it profit a man to gain the whole world and forfeit his soul?” (Mark 8:36). What do our “testimonies” profit us, even if we gain transformed lives, while losing our souls because we do not know who Jesus is? The Christian testimony is that, as Calvin put it, the sinless Son of God became the Son of man, so that the sinful sons of men might become the sons of God. Or as Augustine wrote, “By joining therefore to us the likeness of his humanity, he took away the unlikeness of our unrighteousness; and by being made partaker of our mortality, he made us partakers of his divinity.”6 Do we know the Son of God who became man? Do we rest on the works proper to His deity and to His humanity, united in the person of God the Son? Do we know why He had to be God and man, two natures in one person, so that we might receive eternal life through the God-man personally? Do we testify that “great indeed, we confess, is the mystery of godliness: He was manifested in the flesh, vindicated by the Spirit, seen by angels, proclaimed among the nations, believed on in the world, taken up in glory” (1 Tim. 3:16)?

Editor’s Note: This post is part of a series on Christ as Mediator and was originally published February 22, 2021. Next post.

  1. These four categories proving the divinity of the Son and the Spirit follow the order of WLC 11. ↩︎
  2. Augustine, De Trinitate, NPNF, 3:71. ↩︎

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