Heb 12:24 to Jesus the Mediator of the new covenant, and to the blood of sprinkling that speaks better things than that of Abel.
The Greek word "diatheke" is translated as "covenant" above.
It is the same Greek word found below, which is translated as "testament" in the KJV, but "covenant" in the NKJV.
Heb 8:6 But now He has obtained a more excellent ministry, inasmuch as He is also Mediator of a better covenant, which was established on better promises.
Heb 8:7 For if that first covenant had been faultless, then no place would have been sought for a second.
Heb 8:8 Because finding fault with them, He says: "BEHOLD, THE DAYS ARE COMING, SAYS THE LORD, WHEN I WILL MAKE A NEW COVENANT WITH THE HOUSE OF ISRAEL AND WITH THE HOUSE OF JUDAH—
Heb 8:9 NOT ACCORDING TO THE COVENANT THAT I MADE WITH THEIR FATHERS IN THE DAY WHEN I TOOK THEM BY THE HAND TO LEAD THEM OUT OF THE LAND OF EGYPT; BECAUSE THEY DID NOT CONTINUE IN MY COVENANT, AND I DISREGARDED THEM, SAYS THE LORD.
Heb 8:10 FOR THIS IS THE COVENANT THAT I WILL MAKE WITH THE HOUSE OF ISRAEL AFTER THOSE DAYS, SAYS THE LORD: I WILL PUT MY LAWS IN THEIR MIND AND WRITE THEM ON THEIR HEARTS; AND I WILL BE THEIR GOD, AND THEY SHALL BE MY PEOPLE.
Heb 8:11 NONE OF THEM SHALL TEACH HIS NEIGHBOR, AND NONE HIS BROTHER, SAYING, 'KNOW THE LORD,' FOR ALL SHALL KNOW ME, FROM THE LEAST OF THEM TO THE GREATEST OF THEM.
Heb 8:12 FOR I WILL BE MERCIFUL TO THEIR UNRIGHTEOUSNESS, AND THEIR SINS AND THEIR LAWLESS DEEDS I WILL REMEMBER NO MORE."
(Copied word-for-word from Jeremiah 31:31-34.)
Heb 8:13 In that He says, "A NEW COVENANT," He has made the first obsolete. Now what is becoming obsolete and growing old is ready to vanish away.
Heb 9:15 And for this reason He is the Mediator of the new covenant, by means of death, for the redemption of the transgressions under the first covenant, that those who are called may receive the promise of the eternal inheritance.
(Same covenant as in Hebrews 8:6.)
Heb 9:16 For where there is a testament, there must also of necessity be the death of the testator.
Heb 9:17 For a testament is in force after men are dead, since it has no power at all while the testator lives.
Heb 9:18 Therefore not even the first covenant was dedicated without blood.
You are correct about one thing.
The New Covenant was fulfilled at Calvary.
That account is found in all four Gospels.
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