We are saved by Grace.. Jesus freed us from the law because He came to fulfill it.. so we are not bound by the laws of the OT.. which we could never follow because it is impossible. The OT was preparing the way for The Lamb.. there is no way the blood of an animal could ever cover sin.. It took the blood Christ shed for us on the cross where our sins were nailed to cover every sin forevermore.. In the OT they sacrificed the blood of animals in acknowledgment for their every sin.. They HAD to acknowledge and repent of them to God. Just like when we ask for forgiveness.. Jesus already shed the blood but we HAVE to acknowledge and repent.