Is it possible to enter into covenant relationship with God as an unbeliever? Are there unbelievers in the covenant? Or are there only ever believers in the covenant?
Howdy-
1) Looking at the terms of the
New Covenant (Hebrews 8 quoting Jeremiah 31) Yahweh makes it clear that he will be keeping both parts of the covenant since Israel couldn't keep the terms of the Mosaic Covenant. This New Covenant will make the old one obselete (Hebrews 8:13) and it is a much, much better covenant.
2) We can actually think of this as the "Renewed Covenant" since the Abrahamic Covenant was also kept by Yahweh on both sides and the New Covenant is the completion of God's promise to bless all the nations through Abraham's seed (Genesis 12:1-3)
3) As did all covenants in the Old Testament between Yahweh and his people, the New Covenant requires a blood sacrifice, and in this case it is Christ himself (Hebrews 8:6, 9:11-28).
4) Since it is explicitly Christ's own body and blood that established the covenant (1 Corinthians 11:25) it is only by applying that blood to your life through personal trust in Christ's life and work that you enter into the covenant. It is these who eagerly await his return (Hebrews 9:28), the ones who will be saved.
5) To drive this home, the author of Hebrews says this in chapter 10:19-23,26,29
Therefore, brothers, since we have confidence to enter the holy places by the blood of Jesus, by the new and living way that he opened for us through the curtain, that is, through his flesh, and since we have a great priest over the house of God, let us draw near with a true heart in full assurance of faith, with our hearts sprinkled clean from an evil conscience and our bodies washed with pure water. Let us hold fast the confession of our hope without wavering, for he who promised is faithful.
For if we go on sinning deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins,...How much worse punishment, do you think, will be deserved by the one who has trampled underfoot the Son of God, and has profaned the blood of the covenant by which he was sanctified, and has outraged the Spirit of grace?
To "hold fast to the confession of hope" (Jesus' sacrifice) is connected to trusting Jesus to faithfully keep his promise. There is a clear relational back and forth going on here; Jesus provided the access into covenant relationship, we take hold of the covenant by "holding fast".
6) In Romans 11, Paul says that Gentile "grafting" into the New Covenant promise to Israel is made possible because of Israel's rejection of Jesus, but that if they don't continue in their unbelief, they too will be saved. Again, the Father established the New Covenant in the blood of Jesus, which is why "no one comes to the Father but by me" (John 14:6). But to lay hold of this new life, it is through personal trust in Jesus as the perfect sacrifice (John 6:28-29,40)
As a side note, a blood sacrifice was a
necessary but
not a sufficient condition for Old Testament covenants; two parties had to be willing to enter into the covenant. This is why a marriage ceremony isn't binding if it's coerced, even if the venue, food, and honeymoon have been paid for. Covenants in the Middle East were relational, family producing, affairs. For example, a weak chieftain would take on a filial (literally, son-like) relationship to a stronger king through a covenant in order to gain protection. (For more info, check out Dr. Walter Kaiser's helpful
Toward and Old Testament Theology)