We know that salvation from our sins does not come by keeping the law. As even the Old Testament states in Psalm 143:2 "No one living is righteous before you". And that was a psalm of King David who is declared a "man after" God's "own heart" in 1 Samuel 13:14 and confirmed in the New Testament at Acts 13:22. The New Testament concurs in Romans 3:20 it reads "..by the deeds of the law no flesh will be justified in His sight, for by the law is the knowledge of sin." So the law reveals that we have not kept the law. Now if we accept that this is the truth about us that we have broken God's commandments and sinned and realize we can't be made right by our selves then we may seek God's remedy which is by believing in Christ. The Old Testament declares in Isaiah 53:1 "Who has believed our report?" So Isaiah 53 starts off with belief. Not only that but in the Old Testament in Habakkuk 2:4 it reads "the just shall live by his faith" as is backed up in the New Testament at Romans 1:17. So we have laid down the necessity of faith and belief from the Old Testament and the New Testament. But faith in what?

Let us at this moment consider the report from Isaiah 53 in the Old Testament. I will quote it in its entirety here:

1 Who has believed our report?
      And to whom has the arm of the LORD been revealed?
       2 For He shall grow up before Him as a tender plant,
      And as a root out of dry ground.
      He has no form or comeliness;
      And when we see Him,
      There is no beauty that we should desire Him.
       3 He is despised and rejected by men,
      A Man of sorrows and acquainted with grief.
      And we hid, as it were, our faces from Him;
      He was despised, and we did not esteem Him.
       4 Surely He has borne our griefs
      And carried our sorrows;
      Yet we esteemed Him stricken,
      Smitten by God, and afflicted.
       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.

       6 All we like sheep have gone astray;
      We have turned, every one, to his own way;
      And the LORD has laid on Him the iniquity of us all.
       7 He was oppressed and He was afflicted,
      Yet He opened not His mouth;
      He was led as a lamb to the slaughter,
      And as a sheep before its shearers is silent,
      So He opened not His mouth.
       8 He was taken from prison and from judgment,
      And who will declare His generation?
      For He was cut off from the land of the living;
      For the transgressions of My people He was stricken.

       9 And they made His grave with the wicked—
      But with the rich at His death,
      Because He had done no violence,
      Nor was any deceit in His mouth.
       10 Yet it pleased the LORD to bruise Him;
      He has put Him to grief.
      When You make His soul an offering for sin,
      He shall see His seed, He shall prolong His days,
      And the pleasure of the LORD shall prosper in His hand.
       11 He shall see the labor of His soul,[b]and be satisfied.
      By His knowledge My righteous Servant shall justify many,
      For He shall bear their iniquities.

       12 Therefore I will divide Him a portion with the great,
      And He shall divide the spoil with the strong,
      Because He poured out His soul unto death,
      And He was numbered with the transgressors,
      And He bore the sin of many,
      And made intercession for the transgressors.

Clearly the report that is to be believed is the very report of how one would one day come and "justify many, for He shall bear their iniquities." Who gets "cut off from the land of the living". Now this was written well before the New Testament was written and much of the New Testament is a description of the one who fulfilled Isaiah 53 and the very answer to the question posed in Isaiah 53:8 above of "who will declare his generation?" The answer being the writers of the New Testament and Isaiah 53:1 is quoted once in the Gospel of John and once in Romans 10:16 in the New Testament. And as you read those the report of Jesus in the Gospels and throughout the New Testament you will find that Jesus fits the description in Isaiah 53 quite well. 

So it is clear that one is made right before God by faith in the gospel as both the Old Testament and New Testament concur. But what about all those blessings for obedience and promises of rewards for obedience in the Old Testament and what about the law of God for believers today. Does it apply at all?

It is clear that the Old Testament and New Testament both teach that even though salvation doesn't come through keeping the law but by faith that the law still applies for blessings. And this is made clear in the New Testament as Paul quotes the Old Testament in Ephesians 6:1-3 and applies the Old Testament command and rewards for obedience to New Testament Christians. Let's quote Ephesians 6:1-3 which is a New Testament passage that quotes an Old Testament command.

"Children, obey your parents in the Lord, for this is right. “Honor your father and mother,” which is the first commandment with promise: “that it may be well with you and you may live long on the earth.”

So Paul here is applying one of the 10 commandments from Exodus 20 that was given to Israel on Mount Sinai to children and connects the promise and actually emphasizes the promise as the first commandment with promise as an encouragement for children to obey their parents. So it appears that the 10 commandments still applies to New Testament Christians. These Christians are clearly not Jewish or Israelite (Ephesians 2:11) and clearly no living in the Jewish or Israelite territory (Ephesians 1:1). So the Old Testament still applies for believers today after Christ has come as much as it did for believers in Old Testament times who looked forward to the day that this Christ would come. But in neither time was it meant to be for salvation except to reveal the need of salvation but nor is it to be ignored after we have come to trust Christ alone for salvation.

Now what about the sacrifices and the temple. Jesus said in Matthew 24:2 "“Do you not see all these things? Assuredly, I say to you, not one stone shall be left here upon another, that shall not be thrown down.” He was speaking of the temple that stood in the days of Jesus. The temple was the place where sacrifices were made to atone for the sins of the people. Isaiah 53 as we read above spoke of a time when somebody (who we now know to be Christ) would be the sacrifice. Now that Christ has come and fulfilled Isaiah 53 there is now no more need of the sacrifices that the temple was built for. The destruction of the temple that Jesus prophesied of occurred some 40 years after he prophesied it to be so. work on this sentenceThis gives further evidence that Jesus is indeed the one who fulfilled Isaiah 53 as the Lord has not provided the Old Testament place of sacrifice for sins has stood for some 2000 years now.