Title says it all. Also, just to start off, I am a believer but I always have questions like these pop up in my head when I read the OT. I was reading the Psalms tonight and the Sons of Korah and David both talk about their delight in the Lord for his forgiveness of sins and how He makes those who love Him righteous. If God forgave the sins of those who love Him before sending His Son, and made people righteous, then why did we need Jesus in the first place?
Gen 15:5-6 NASB 5 And He took him outside and said, "Now look toward the heavens, and count the stars, if you are able to count them." And He said to him, "So shall your SEED be." 6 Then he believed in the LORD; and He credited it to him as righteousness.
That "credit" of righteousness? Who paid for that? Who redeemed that? Where did that righteousness come from?
Gal 3:13-18 NASB 13 Christ redeemed us from the curse of the Law, having become a curse for us for it is written, "CURSED IS EVERYONE WHO HANGS ON A TREE" 14 in order that in Christ Jesus the blessing of Abraham might come to the Gentiles, so that we would receive the promise of the Spirit through faith. 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.
That righteousness came from Jesus Christ. Jesus gave up his righteousness in exchange for our sin and the specifically the sin of Abraham. Those who have the same faith in the gospel of Jesus Christ that Abraham had are considered the "sons" of Abraham. God promised that the righteousness given to Abraham would be an everlasting inheritance by the children of Abraham.
Gal 3:6-9 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. 29 And if you belong to Christ, then you are Abraham's descendants, heirs according to promise.
Rom 4:8-13, 16-17 NASB 8 "BLESSED IS THE MAN WHOSE SIN THE LORD WILL NOT TAKE INTO ACCOUNT." 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. ... 16 For this reason [it is] by faith, in order that [it may be] in accordance with grace, so that the promise will be guaranteed to all the descendants, not only to those who are of the Law, but also to those who are of the faith of Abraham, who is the father of us all, 17 (as it is written, "A FATHER OF MANY NATIONS HAVE I MADE YOU") in the presence of Him whom he believed, [even] God, who gives life to the dead and calls into being that which does not exist.
Quite simply, the purpose of Jesus was to qualify (by the Law of Moses) as the first righteous person in existence since the Fall so that SOMEONE could bring righteousness into the equation. The sacrificial system allowed him to give up that righteousness as a substitutionary atonement for sin. God's promise to Abraham that all of his (spiritual) descendants would inherit the righteousness he was credited was how the righteousness of One man (Jesus) multiplied to many.
Rom 5:19 NASB 19 For as through the one man's disobedience the many were made sinners, even so through the obedience of the One the many will be made righteous.
Jesus purpose is summed up in the book of Revelation:
Rev 5:1-10 NASB 1 I saw in the right hand of Him who sat on the throne a book written inside and on the back, sealed up with seven seals. 2 And I saw a strong angel proclaiming with a loud voice, "Who is worthy to open the book and to break its seals?" 3 And no one in heaven or on the earth or under the earth was able to open the book or to look into it. 4 Then I [began] to weep greatly because no one was found worthy to open the book or to look into it; 5 and one of the elders said to me, "Stop weeping; behold, the Lion that is from the tribe of Judah, the Root of David, has overcome so as to open the book and its seven seals." 6 And I saw between the throne (with the four living creatures) and the elders a Lamb standing, as if slain, having seven horns and seven eyes, which are the seven Spirits of God, sent out into all the earth. 7 And He came and took the book out of the right hand of Him who sat on the throne. 8 When He had taken the book, the four living creatures and the twenty-four elders fell down before the Lamb, each one holding a harp and golden bowls full of incense, which are the prayers of the saints. 9 And they sang a new song, saying, "Worthy are You to take the book and to break its seals; for You were slain, and purchased for God with Your blood [men] from every tribe and tongue and people and nation. 10 "You have made them [to be] a kingdom and priests to our God; and they will reign upon the earth."
