The Old Covenant provided sacrifices to be performed over and over for sins. The New Covenant also provided a blood offering for sins, but the two are quite different. Heb 10:3-4 (ESV) says, “But in these sacrifices there is a reminder of sins every year. For it is impossible for the blood of bulls and goats to take away sins.”
Under the Old Covenant the sacrifices had to be completed year by year, day by day, over and over. Sin was not actually removed, it was merely covered. We too often make the mistake of believing sins were actually removed by these sacrifices, but such offerings could never remove sins.
There was only one sacrifice ever offered that actually removed sins. This offering was the last one performed under the Old Covenant—the sacrifice of Christ. Once this was completed sins were removed (not just covered) and the Old Covenant sacrificial system was abolished. The New Covenant was ushered in.
There was only one sacrifice efficacious for the removal and forgiveness of sins. All the others were merely a shadow of the true sacrifice for sins (Heb 10:1). Don’t make the mistake of thinking anyone was actually forgiven for offering bulls or lambs. Instead those who made these offerings had their sins “laid aside” or “overlooked” without punishment, until God offered the only sacrifice that would forgive us and them. No one in any age has ever been saved outside of Jesus Christ. No one in any age will ever be saved outside of Jesus Christ. Jesus is not an alternative route of salvation offered by God. Jesus is the only route of salvation offered by God.