This is the law for expiating the guilt of a national sin, by a sin offering. If the leaders of the people, through mistake concerning the law, caused them to err, when the mistake was discovered an offering must be brought, that wrath might not come upon the whole congregation. Observe, 1. It is possible that the church may err, and that her guides may mislead her. It is here supposed that the whole congregation may sin, and sin through ignorance. God will always have a church on earth; but he never said it should be infallible, or perfectly pure from corruption on this side heaven. 2. When a sacrifice was to be offered for the whole congregation, the elders were to lay their hands upon the head of it (three of them at least), as representatives of the people and agents for them. The sin we suppose to have been some common custom, taken up and used by the generality of the people, upon presumption of its being lawful, which afterwards, upon search, appeared to be otherwise. In this case the commonness of the usage received perhaps by tradition from their fathers, and the vulgar opinion of its being lawful, would not so far excuse them from sin but that they must bring a sacrifice to make atonement for it. There are many bad customs and forms of speech which are thought to have no harm in them, and yet may bring guilt and wrath upon a land, which therefore it concerns the elders both to reform and to intercede with God for the pardon of, Joel 2:16. 3. The blood of this sin-offering, as of the former, was to be sprinkled seven times before the Lord, Lev. 4:17. It was not to be poured out there, but sprinkled only; for the cleansing virtue of the blood of Christ was then and still is sufficiently signified and represented by sprinkling, Isa. 52:15. It was to be sprinkled seven times. Seven is a number of perfection, because when God had made the world in six days he rested the seventh; so this signified the perfect satisfaction Christ made, and the complete cleansing of the souls of the faithful by it; see Heb. 10:14. The blood was likewise to be put upon the horns of the incense-altar, to which there seems to be an allusion in Jer. 17:1; where the sin of Judah is said to be graven upon the horns of their altars. If they did not forsake their sins, the putting of the blood of their sin-offerings upon the horns of their altars, instead of taking away their guilt, did but bind it on the faster, perpetuated the remembrance of it, and remained a witness against them. It is likewise alluded to in Rev. 9:13; where a voice is heard from the four horns of the golden altar; that is, an answer of peace is given to the prayers of the saints, which are acceptable and prevalent only by virtue of the blood of the sin-offering put upon the horns of that altar; compare Rev. 8:3. 4. When the offering is completed, it is said, atonement is made, and the sin shall be forgiven, Lev. 4:20. The promise of remission is founded upon the atonement. It is spoken here of the forgiveness of the sin of the whole congregation, that is, the turning away of those national judgments which the sin deserved. Note, The saving of churches and kingdoms from ruin is owing to the satisfaction and mediation of Christ.