The Testament is no Testament, nor valid in Law, except the Testatator be dead. No man can sue by Law tested goods, if the Testator himself be living. Nor can we have right to a new heart, forgiveness, perseverance, eternal life, to grace and glory, except Christ our Testator had died. But because the Tested goods are more then goods left to us in Testament; they are left to us by such a Testament as is both a Testament and a death perfectly meritorious (this is superadded to the nature of a Testament, and beyond all Testaments) yea a death which is a price to ransom us from the wrath to come; Therefore Christ so dying in our stead, of justice meriteth that the friends should have these goods, though they belong by mere grace and free promise, to the friends. Now this is a most clear ground: Christ hath a well purchased right, by giving a condign price for the goods, and blessings promised in the Covenant of Grace to us: This right he hath by paying a price, laying down his life for us. This buying is not by necessity of nature, of justice but by a voluntary, free and uncompessed agreement and Covenant, John 10. 18. Isaiah 53. 6. No man can exact upon him Psal. 89. 22. (2.) If the Old Testament was confirmed by the blood of beasts, then must the New Testament be confirmed by the blood of Christ prefigured in these. But the Old Testament was so confirmed, Heb. 9. v. 18, 19 20 21, 22, [23.] Ergo now neither Testament nor Covenant was confirmed by blood simply, but by the blood of a living creature slain.
3. Hence the making of a Covenant was by cutting a calf or a beast in twain, and passing between the parts thereof, Jer. 34. 18. and so they entered into a curse, Nehem. 10. 29. devoted themselves to destruction, wishing they might be cut in twain (which is a strange kind of death, Mat. 24. 51. if they should break the Covenant. Hence the Phrase of striking a Covenant. So the Romans slew a Sow: So the Romans and Albani made a Covenant, as Livius. A Herald or Officer at Arms slew the beast, and prayed a curse on the people of Rome, that they might the same way be stricken, if they should break the Covenant. Its like they had it from the Jews. So Christ died to ratify and confirm the Covenant, Exod. 24. 6. This is the blood of the Covenant. Now the Covenant hath no blood, this blood of slain beasts (for it is a figurative speech) is a sign confirming the Covenant that believers shall have remission of sins in that blood of Christ which is shaddowed forth by the blood of these beasts. So Christ the great Shepherd of the flock Heb. 10. 13. is said to be brought from the dead, ἐν αἵματι by the blood of the everlasting Covenant. Junius the Article is understood: Or as the Hebrew Phrase, ב is put for ἐν, as Calvin and Piscator. The question may be, How did God bring Christ again from the death by the blood of the everlasting Covenant, had the blood of Christ any influence to bring himself back from the dead? Or did he, by dying, merit his own resurrection?
Ans. Some read the word thus, and shun the Question, The God of peace who brought again from the dead the great sheepherd of the sheep: Understanding, ὀντα, being the great sheepherd or feeder, by the blood of the everlasting Covenant. So Beza, who makes these words ἐν ἅιματι, to be referred to ποιμένα: So as Christs right to be Pastor is in, and by his blood and suffering. And the words, ἐν ἅιματι, so is not to be constructed with the particle, ἀναγαγὼν: But Beza confesseth, that he changed the situation of the words. But if Christ be made a Pastor and feeder of the sheep by the blood of the eternal Covenant: then is he called to be a Pastor by Covenant. And what influence hath his death in his Pastoral Office? Is it by way of merit? Or did Christ merit to himself? Hardly, if not curiously can we say that, though I nothing doubt but Christ gave perfect obedience as man to the Covenant of Works, and he did merit as man, iure operum [by the law of works], life eternal, the way that Adam should have merited life eternal, so he had never fallen….
—Samuel Rutherford, The Covenant Of Life Opened (1654; republished 1655), 318–20.