Reading through the Bible together
The sacrifices in Leviticus 1-3 were voluntary, but the sin and trespass offerings (Lev 4-5) were required when human imperfections could affect God’s sanctuary or holy things associated with it. So the sin and trespass offerings helped to maintain the presence of God among His people. The burnt offering was the basic atoning sacrifice (Job 42:8; Lev 1:4), but the sin and trespass offerings were added to deal with special kinds of cases. The sin offering, better termed “purification offering,” purified offerers from lesser (usually unintentional) sins and from physical ritual impurities (Lev 12, 14-15). The physical impurities were not acts of sin, but represented the human state of mortality resulting from sin.
Uniquely, the blood of a sin offering was placed on the horns, that is, the highest points, of the altar of incense (when the high priest or whole community sinned) or of the outer altar (in all other cases). This showed the importance of the blood, which ransomed the life of the offerer (Lev 17:11) and pointed to Christ, who would come and provide “redemption through His blood” (Eph 1:7) and give “His life a ransom for many” (Matt 20:28). Christ not only provides forgiveness for our acts of sin, but healing from our state of mortality resulting from sin (compare Ps 103:2-3) so that we can enjoy eternal life (Rom 6:23).