For thousands of years, the priests of the temples sacrificed animals to atone for our sins. I cannot imagine how many animals were killed, but because they were not the perfect sacrifice, it never provided the perfect atonement necessary for us. We received the perfect sacrifice from Jesus Christ on the cross. The prior sacrifices were a constant reminder of our sinful nature and that we would never receive the complete atonement we craved. It took our Great High Priest, Jesus Christ, to provide the necessary perfect sacrifice. The moment He did the first covenant was abolished, and the new covenant, the atonement of our sins through the blood of Christ, was installed.
What a wonderful gist He gave us.
God Loves You And So Do I