Exodus 30:10

10.And Aaron shall make an atonement. We should observe here the correspondence between the two altars; for, as the Israelites were admonished that the sacrifices would not please God, unless all uncleanness were wiped away by pure and holy prayers, so also the altar of incense was purified by the sprinkling of blood, that they might learn that their prayers obtained acceptance through sacrifices. Although this was only done once a year, yet it was daily to be called to mind, in order that they might offer the death of Christ by faith and prayer, (153) and yet might know that their prayers had no sweet savor, unless in so far as they were sprinkled with the blood of atonement.