This is an excellent question and as we shall see, it did indeed “come into effect…after the death of Jesus.” We shall see that believers in Christ are already under the spiritual blessings of this blessed covenant. But we shall also see that the New Covenant was actually a promise made to Israel and in a future day believing Jews will receive all the blessings of the New Covenant. 

When the Lord Jesus instituted the Lord’s Supper, He took a cup of wine and said, “This cup is the NEW COVENANT in My BLOOD, which is shed for you” (Luke 22:20). In saying this He was anticipating His death on the cross. Within hours Jesus was on the cross and after He was judged for man’s sin He cried out “It is finished” and then we read, “And bowing His head, He gave up His spirit” (John 19:30).  Jesus had literally “laid down His life” (see John 10:17-18) so God could offer sinners eternal life (see John 10:17-18, 27-28). Yet there was one more thing that had to be accomplished and we see this in verse 34, “But one of the soldiers pierced His side with a spear, and immediately BLOOD and water came out.” In this violent act “the blood of Jesus was shed” to prove that He had truly died and to form the basis for the New Covenant.

It is vital to understand exactly what the New Covenant is. The “Old Covenant” was the “Law” which was given to Moses on Mount Sinai and then to the nation of Israel. It was an agreement between God and Israel where blessings were promised to them IF they were obedient to all the commandments in “the Law.” The Law required perfect righteousness and condemned the lawbreaker. Because of their sinful hearts Israel was unable to keep the Law and thus we read in Jeremiah 31:32, “My covenant which they broke.” By contrast, the New Covenant is an “UNCONDITIONAL covenant of pure grace,” where instead of God demanding perfect righteousness and condemning the sinner who breaks the Law, He imputes righteousness to the believing sinner through the death and blood-shedding of His beloved Son. This is beautifully seen in Romans 3:21-25a, “But now the righteousness of God apart from the law is revealed…even the righteousness of God, through FAITH IN JESUS CHRIST, to all and on all who believe. For there is no difference; for all have sinned and come short of the glory of God, being JUSTIFIED FREELY BY HIS GRACE THROUGH THE REDEMPTION THAT IS IN CHRIST JESUS, whom God see forth as a propitiation BY HIS BLOOD, THROUGH FAITH.”

We have just seen from Romans chapter 3 that the blessings of REDEMPTION and JUSTIFICATION were given to all believers right after Christ’s death, so in that sense the effects of the New Covenant were immediate. But as mentioned at the outset, the New Covenant was a definite promise made to Israel and they won’t receive the fulfillment of it until they repent and believe on the Lord Jesus Christ. Ever since Christ’s death, the nation, as a whole, has been in a state of “spiritual blindness” and thus they reject the good news of the New Covenant. They believe that Christ is the SOURCE of all their problems but in a coming day they will see that He is the REMEDY for all their problems and then God will officially make the New Covenant with them. We read of this in Romans 11:25-27, “For I do not desire, brethren, that you should be ignorant of this mystery, lest you should be wise in your own opinion, that blindness in part has happened to Israel until the fullness of the Gentiles has come in. And so all Israel will be saved, as it is written: ‘The Deliverer will come out of Zion, and He will turn away ungodliness from Jacob; for this is My COVENANT WITH THEM, when I take away their sins.’” At that time, the scales of unbelief will be lifted from the eyes of a Jewish remnant who repent of their sins. They will finally see the truth of Isaiah 53:5, “But He was wounded for our transgressions, He was bruised for our iniquities; the chastisement for our peace was upon Him, and by His stripes we are healed.” They will be blessed with “forgiveness of sins,” “justification,” and “a New Birth,” and will finally realize that they owe every blessing (which will also include “material blessings”) to God’s grace manifested in the sacrificial death of the Lord Jesus Christ. I would encourage you to read more of the New Covenant that will be made with Israel in Jeremiah 31:31-34 and Ezekiel 36:26-30.  (471.5)  (DO)