See the marginal references.

An atonement - once in a year - On the tenth day of the seventh month. See Leviticus 16:18 (note), etc., and the notes there. See Clarke on Leviticus 16:21 (note), etc.

And Aaron shall make an atonement upon the horns of it once in a year,.... On the day of atonement, as the Targum of Jonathan, and so Jarchi and Aben Ezra explain it; and the atonement here referred to seems to be an atonement for the altar itself, see Leviticus 16:18 and as the altar of burnt offering was first expiated and then used, Exodus 29:36 so it seems the altar of incense had not only an atonement made on it, but for it: and this was done

with the blood of the sin offering of atonement; by sprinkling the blood of that offering upon the horns of it, as we learn from the afore mentioned place; and this shows that Christ's mediation and intercession is founded upon the virtue of his blood, and the efficacy of his atoning sacrifice, see 1 John 2:1.

once in the year shall he make atonement upon it, throughout your generations; which proves the insufficiency of all legal sacrifices of themselves to take away sin, since every year, as the apostle observes, there was a remembrance of it, Hebrews 10:3.

it is most holy unto the Lord; either the atonement made on the day of atonement, which was a most holy part of service, and pointed at the great atonement made by the most Holy One, the Son of God; or this altar thus expiated, and devoted to sacred use, was reckoned a most sacred one to the Lord, and so was to have nothing offered upon it but what he ordered; with which Jarchi agrees in his note,"the altar is sanctified to these things only, and not to any other service.''

Once a year Aaron was to expiate the altar of incense with the blood of the sin-offering of atonement, because it was most holy to the Lord, that is to say, as is expressly observed in the directions concerning this expiatory act (Leviticus 16:18-19), to purify it from the uncleannesses of the children of Israel. כּפּר, with על objecti constr., signifies literally to cover over a thing, then to cover over sin, or make expiation. In the second clause we have "upon it" (the altar) instead of "upon the horns of it," because the altar itself was expiated in its horns. The use of מן in מדּם is to be explained on the ground that only a part of the blood of the sin-offering was smeared with the finger upon the horns. (For further remarks, see at Leviticus 16:18-19.) The term "most holy" is not only applied to this altar, in common with the inner division of the tabernacle (Exodus 26:33), but also to the altar of burnt-offering (Exodus 29:37; Exodus 40:10), and all the vessels of the sanctuary (Exodus 30:29), which were anointed with holy oil; then to the whole of the tabernacle in its holiest aspect (Numbers 18:10); and lastly, to all the sacrifices, which were given up entirely to Jehovah (see at Leviticus 2:3); - consequently to everything which stood in so intimate a relation to Jehovah as to be altogether removed, not only from use and enjoyment on the part of man, but also from contact on the part of unsanctified men. Whoever touched a most holy thing was sanctified thereby (compare Exodus 30:29 with Exodus 29:37).

And Aaron shall make an atonement upon the horns of it once in a year with the blood of the sin offering of atonements: once in the year shall he make atonement upon it throughout your generations: it is most holy unto the LORD.

30:10 This altar was purified with the blood of the sin - offering put upon the horns of it every year, upon the day of atonement. See Lev 16:18,19. The high priest was to take this in his way as he came out from the holy of holies. This was to intimate, that the sins of the priests who ministered at this altar, and of the people for whom they ministered, put a ceremonial impurity upon it, from which it must be cleansed by the blood of atonement. This altar typified the mediation of Christ: the brazen altar in the court was a type of Christ dying on earth; the golden altar in the sanctuary was a type of Christ interceding in heaven. This altar was before the mercy - seat, for Christ always appears in the presence of God for us; and his intercession is unto God of a sweet smelling savour. And it typified the devotions of the saints, whose prayers are said to be set forth before God as incense, Psa 141:2. As the smoke of the incense ascended, so must our desires, being kindled with the fire of holy love. When the priest was burning incense the people were praying, Luke 1:10, to signify that prayer is the true incense. This incense was a perpetual incense, for we must pray always. The lamps were dressed or lighted at the same time that the incense was burnt, to teach us that the reading of the scriptures (which are our light and lamp) is a part of our daily work, and should ordinarily accompany our prayers and praises. The devotions of sanctified souls are well - pleasing to God, of a sweet - smelling savour; the prayers of saints are compared to sweet odours, Rev 5:8, but it is the incense which Christ adds to them that makes them acceptable; and his blood that atones for the guilt which cleaves to our best services. Yet if the heart and life be not holy, even incense is an abomination, Isa 1:13.

Margin atonement

See Scofield Note: "Ex 29:33".

30:1-10 The altar of incense represented the Son of God in his human nature, and the incense burned thereon typified his pleading for his people. The continual intercession of Christ was represented by the daily burning of incense thereon, morning and evening. Once every year the blood of the atonement was to be applied to it, denoting that the intercession of Christ has all its virtue from his sufferings on earth, and that we need no other sacrifice or intercessor but Christ alone.