Westminster Project 7.4

4. This covenant of grace is frequently set forth in Scripture by the name of a testament, in reference to the death of Jesus Christ, the testator, and to the everlasting inheritance bequeathed by it, with all the things belonging to it. 
(WCF 7.4)

We have been examining the nature of the covenants that God made with humanity. First, there was the covenant of works, established in Eden with our first parents. However, this covenant was broken through their sin, as they disregarded God’s command not to eat from the tree of the knowledge of good and evil. As we’ve seen, the curse of death was brought upon them, making all who descended from them dead in trespasses and sins—unable to live according to the terms of that first covenant.

We then saw that, because humanity was incapacitated, God graciously made a second covenant with us—what the Confession refers to as the covenant of grace. It is called that because grace stands at the heart of the entire arrangement. It came by God’s undeserved mercy and love: He made a covenant with sinners by His grace alone, hence the name.

At this point, the Confession begins to define some important terms for us, stating: This covenant of grace is frequently set forth in Scripture by the name of a testament. Why point this out? Because the Westminster theologians wanted us to grasp significant biblical themes using biblical language. Put another way, while the language of "covenant" is essential, the Bible often uses the word testament—particularly in the King James Version, which the Westminster Assembly used when composing the Confession.

You may notice in our Bibles that we have two main sections: the Old Testament and the New Testament. The word testament is simply the English rendering of the Greek word behind it, but theologian Chad Van Dixhoorn suggests there is more to it. He writes, “The term ‘Testament’ … invokes the idea of a testator, in Jesus Christ, and of an everlasting inheritance with all things belonging to it.” In other words, while the Westminster theologians used covenantal language to explain their theology (and covenant is certainly a biblical term—see Hebrews 9:15, for example), they also wanted the idea of a will and testament to shape our understanding. And testament is, indeed, a word employed by biblical writers for good reason.

This was clearly the preacher’s point in Hebrews 9 when he said:
“In the case of a will, it is necessary to prove the death of the one who made it, because a will is in force only when somebody has died; it never takes effect while the one who made it is living.”

His point? Jesus had to die for His will and testament to take effect. So we might ask—what was His will?

Before going to the cross, Jesus spoke to His disciples, saying:
“Do not let your hearts be troubled. You believe in God; believe also in me. My Father’s house has many rooms; if that were not so, would I have told you that I am going there to prepare a place for you? And if I go and prepare a place for you, I will come back and take you to be with me that you also may be where I am. You know the way to the place where I am going.”
[...]
“Peace I leave with you; my peace I give you. I do not give to you as the world gives. Do not let your hearts be troubled and do not be afraid.” (John 14:1–3, 27)

God has made a covenant, and a covenant is ratified when the testator sheds their blood so that their will might come into effect. God’s will for us is that we might have peace—not just any peace, but everlasting peace with Him. That peace came through the death of Jesus on the cross for all His people. That’s exactly how WCF 7.4 concludes, referring to the death of Jesus Christ, the testator:
“[We are given] the everlasting inheritance bequeathed by it, with all the things belonging to it.”