The difference between the Old and New Covenants
The Old Covenant entailed, for mankind, the pursuit of legal acceptance before God through the strength, energy and capacity of their human flesh. The New Covenant is not like the Old Covenant. Christ did not offer Himself on behalf of mankind so that they would have a more enduring legal acceptance before God. He established a new covenant that operates differently from the Old Covenant.
In the New Covenant, the efficacy of atonement is only by the blood of sprinkling upon the conscience. The whole world was reconciled to God through the death of Christ on their behalf. However, a person is only saved by receiving His life, which is in His blood. Rom 5:10. Lev 17:11. This blood is given to be their life, through the process of sprinkling. It must be sprinkled on their conscience if they are to be recovered to their predestination as a son of God, to serve the living God. Heb 9:14. This is the only way in which the redemption that is in Christ can be appropriated by a person.
It was for this purpose that Christ was set forth, before the eyes of all, as a propitiation, or mercy seat. We recall that under the Old Covenant, the mercy seat was where the blood of bulls and goats was sprinkled for the purpose of making atonement for the children of Israel, once a year. If Christ is the mercy seat, and atonement requires the sprinkling of our heart, then we must be joined heart to heart with Christ in the fellowship of His offering and sufferings. In this fellowship, as the blood is sprinkled on Christ, the Mercy Seat, it is sprinkled on our heart. By this means, His life is given to us to be our life. Gal 2:20.