The new covenant began when Christ sacrificed his blood at Calvary.
Agree or disagree?
The new covenant was put into full effect at the cross, but it was first established with Abraham.
[Gen 17:4, 7 NASB] 4 "As for Me, behold, My covenant is with you, And you will be the father of a multitude of nations. ... 7 "I will establish My covenant between Me and you and your descendants after you throughout their generations for an everlasting covenant, to be God to you and to your descendants after you.
[Gal 3:6-9, 15-18 NASB] 6 Even so Abraham BELIEVED GOD, AND IT WAS RECKONED TO HIM AS RIGHTEOUSNESS. 7 Therefore, be sure that it is those who are of faith who are sons of Abraham. 8 The Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel beforehand to Abraham, [saying,] "ALL THE NATIONS WILL BE BLESSED IN YOU." 9 So then those who are of faith are blessed with Abraham, the believer. ... 15 Brethren, I speak in terms of human relations: even though it is [only] a man's covenant, yet when it has been ratified, no one sets it aside or adds conditions to it. 16 Now the promises were spoken to Abraham and to his seed. He does not say, "And to seeds," as [referring] to many, but [rather] to one, "And to your seed," that is, Christ. 17 What I am saying is this: the Law, which came four hundred and thirty years later, does not invalidate a covenant previously ratified by God, so as to nullify the promise. 18 For if the inheritance is based on law, it is no longer based on a promise; but God has granted it to Abraham by means of a promise.
[Gal 4:22-31 NASB] 22 For it is written that Abraham had two sons, one by the bondwoman and one by the free woman. 23 But the son by the bondwoman was born according to the flesh, and the son by the free woman through the promise. 24 This is allegorically speaking, for these [women] are two covenants: one [proceeding] from Mount Sinai bearing children who are to be slaves; she is Hagar. 25 Now this Hagar is Mount Sinai in Arabia and corresponds to the present Jerusalem, for she is in slavery with her children. 26 But the Jerusalem above is free; she is our mother. 27 For it is written, "REJOICE, BARREN WOMAN WHO DOES NOT BEAR; BREAK FORTH AND SHOUT, YOU WHO ARE NOT IN LABOR; FOR MORE NUMEROUS ARE THE CHILDREN OF THE DESOLATE THAN OF THE ONE WHO HAS A HUSBAND." 28 And you brethren, like Isaac, are children of promise. 29 But as at that time he who was born according to the flesh persecuted him [who was born] according to the Spirit, so it is now also. 30 But what does the Scripture say? "CAST OUT THE BONDWOMAN AND HER SON, FOR THE SON OF THE BONDWOMAN SHALL NOT BE AN HEIR WITH THE SON OF THE FREE WOMAN." 31 So then, brethren, we are not children of a bondwoman, but of the free woman.
Hebrews 8:6
But now He has obtained a more excellent ministry, by as much as He is also the mediator of a better covenant, which has been enacted on better promises.
7 For if that first covenant had been faultless, there would have been no occasion sought for a second.
8 For finding fault with them, He says, “BEHOLD, DAYS ARE COMING, SAYS THE LORD, WHEN I WILL EFFECT A NEW COVENANT WITH THE HOUSE OF ISRAEL AND WITH THE HOUSE OF JUDAH;
9 NOT LIKE THE COVENANT WHICH I MADE WITH THEIR FATHERS ON THE DAY WHEN I TOOK THEM BY THE HAND TO LEAD THEM OUT OF THE LAND OF EGYPT; FOR THEY DID NOT CONTINUE IN MY COVENANT, AND I DID NOT CARE FOR THEM, SAYS THE LORD.
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 INTO THEIR MINDS, AND I WILL WRITE THEM ON THEIR HEARTS. AND I WILL BE THEIR GOD, AND THEY SHALL BE MY PEOPLE.
12 “FOR I WILL BE MERCIFUL TO THEIR INIQUITIES, AND I WILL REMEMBER THEIR SINS NO MORE.”
13 When He said, “A new covenant,” He has made the first obsolete. But whatever is becoming obsolete and growing old is ready to disappear.
[Rom 4:9-13 NASB] 9 Is this blessing then on the circumcised, or on the uncircumcised also? For we say, "FAITH WAS CREDITED TO ABRAHAM AS RIGHTEOUSNESS." 10 How then was it credited? While he was circumcised, or uncircumcised? Not while circumcised, but while uncircumcised; 11 and he received the sign of circumcision, a seal of the righteousness of the faith which he had while uncircumcised, so that he might be the father of all who believe without being circumcised, that righteousness might be credited to them, 12 and the father of circumcision to those who not only are of the circumcision, but who also follow in the steps of the faith of our father Abraham which he had while uncircumcised. 13 For the promise to Abraham or to his descendants that he would be heir of the world was not through the Law, but through the righteousness of faith.
We see very clearly then, that the promise (covenant) to Abraham was the covenant for being made righteous through faith. This was the covenant fulfilled by Jesus at the cross, not created at the cross.
[Rom 8:15-17 NASB] 15 For you have not received a spirit of slavery leading to fear again, but you have received a spirit of adoption as sons by which we cry out, "Abba! Father!" 16 The Spirit Himself testifies with our spirit that we are children of God, 17 and if children, heirs also, heirs of God and fellow heirs with Christ, if indeed we suffer with [Him] so that we may also be glorified with [Him.]
[Isa 54:1 NASB] 1 "Shout for joy, O barren one, you who have borne no [child;] Break forth into joyful shouting and cry aloud, you who have not travailed; For the sons of the desolate one [will be] more numerous Than the sons of the married woman," says the LORD.
The adopted children of Abraham (and therefore inheritors of the righteousn given to Abraham for his faith in the gospel of Jesus Christ) will be more numerous than the physical descendants. Remember, the covenant to Abraham was for him to be the father of MANY nations, not just the one nation. The everlasting covenant in Genesis 17:7 was to those descendants from many nations - the descendants who were of the same faith in the gospel as Abraham.
