Since God provided for the forgiveness of sins in the Old Testament, why do we need Jesus? I thought of this when I was researching this question.



Leviticus 4 goes into great detail about the sacrifice that must be made in order for a sin to be forgiven.  However, we see here that God actually provided a way for these sins to be forgiven.

Specifically, Leviticus 16 shows that this sacrifice and the Day of Atonement did provide forgiveness of sins:


  Leviticus 16:30 (NIV)Emphasis added
  because on this day atonement will be made for you, to cleanse you. Then, before the LORD, you will be clean from all your sins.


Now, Jews no longer provide sacrifices for the forgiveness of sins, however God has still provided a way for these sins to be forgiven. (See Why don't Jews sacrifice animals anymore? for more information.)

So, if God has previously given us a way to have forgiveness of our sins, why did he send Jesus to be our ultimate sacrifice?

Edit: 
I believe that there is some doctrinal basis for this.  I'm not sure which specific doctrine would best be applied to this, but I am seeking a mainstream Protestant doctrine on the matter.
Actually, it never worked.


  Hebrews 10:4 (ESV)
  For it is impossible for the blood of bulls and goats to take away sins.


All the OT sacrifices were useless in an of themselves. What they did all along was not actually solve something but point people to the idea that something needed to be solved and the way that had to happen was through sacrifice. All the OT sacrificial rules only served to point us to Christ, who was already arranged as the Lamb to come.

In other words, the forgiveness for sins that God "provided" in the Old Testament was through Jesus from day one, so you can't just take him out of the picture. There isn't another way.

See also: How were people saved before ~33AD?