Carl Friedrich Keil and Franz Delitzsch Old Testament Commentary

In the future, the priest who was anointed and set apart for the duty of the priesthood in his father's stead, i.e., the existing high priest, was to perform the act of expiation in the manner prescribed, and that "once a year." The yearly repetition of the general atonement showed that the sacrifices of the law were not sufficient to make the servant of God perfect according to this own conscience. And this imperfection of the expiation, made with the blood of bullocks and goats, could not fail to awaken a longing for the perfect sacrifice of the eternal High Priest, who has obtained eternal redemption by entering once, through His own blood, into the holiest of all (Heb 9:7-12). And just as this was effected negatively, so by the fact that the high priest entered on this day into the holiest of all, as the representative of the whole congregation, and there, before the throne of God, completed its reconciliation with Him, was the necessity exhibited in a positive manner for the true reconciliation of man, and his introduction into a perfect and abiding fellowship with Him, and the eventual realization of this by the blood of the Son of God, our eternal High Priest and Mediator, prophetically foreshadowed. The closing words in Lev 16:34, "and he (i.e., Aaron, to whom Moses was to communicate the instructions of God concerning the feast of atonement, Lev 16:2) did as the Lord commanded Moses," are anticipatory in their character, like Exo 12:50. For the law in question could not be carried out till the seventh month of the current year, that is to say, as we find from a comparison of Num 10:11 with Exo 40:17, not till after the departure of Israel from Sinai.