Exodus 30:10

10 Once a year Aaron shall make atonement on its horns. This annual atonement must be made with the blood of the atoning sin offeringa for the generations to come. It is most holy to the LORD.”

Read Exodus 30:10 Using Other Translations

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.
Aaron shall make atonement on its horns once a year. With the blood of the sin offering of atonement he shall make atonement for it once in the year throughout your generations. It is most holy to the LORD."
“Once a year Aaron must purify the altar by smearing its horns with blood from the offering made to purify the people from their sin. This will be a regular, annual event from generation to generation, for this is the LORD ’s most holy altar.”

What does Exodus 30:10 mean?

John Gill's Exposition of the Bible
Exodus 30:10

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 Leviticus 16:19 ) and as the altar of burnt offering was first expiated and then used, ( Exodus 29:36 Exodus 29:37 ) 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 1 John 2:2 )

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 Hebrews 10:4 )

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.''
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