Hebrews 9:15–17

    And for this cause he is the mediator of the new testament, that by means of death, for the redemption of the transgressions that were under the first testament, they which are called might receive the promise of eternal inheritance.
    For where a testament is, there must also of necessity be the death of the testator.
    For a testament is of force after men are dead: otherwise it is of no strength at all while the testator liveth.

Jesus is called the Mediator of the New Testament, and this passage explains why His death was necessary. A testament, or will, does not take effect while the one who made it is still living. It becomes operative only after death. So for the blessings of the New Covenant to be released, Christ had to die.

That is part of what makes the Cross so significant. His death was not only a sacrifice for sin. It was also the moment when the promised inheritance of the New Covenant was put into effect for those who are called.

In everyday life, wills can create confusion. After someone dies, people may gather to sort out what was meant, who receives what, and how the instructions are to be carried out. The one person who could clear up every question is no longer present to explain it.

But that is not the case with Jesus.

He is unique because He is not only the One whose death brought the New Covenant into force. He is also the risen Lord who continues to oversee and apply what He secured. He died to establish the covenant, and He rose again to minister its benefits to His people.

That means believers are not left trying to interpret God’s promises on their own, as though Christ were absent and unreachable. By the Holy Spirit, He is present with His people, guiding them in the reality of the covenant He established.

So the wonder of the New Covenant is not only that it was purchased by His death, but that it is personally carried forward by His living presence. He is both the One who made it possible and the One who leads His people in it.

Because of that, the inheritance promised in this passage is not uncertain. It rests on a covenant secured by Christ’s death and made living and active by His resurrection.