Today's readings are Psalm 119.129-138, Leviticus 9.1-24, and Luke 9.18-36.
In Leviticus 9.7 Moses tells Aaron to approach God's altar with his offerings. He says this offering that Aaron will make is a real offering which makes atonement for sin. It is effective. With his offering Aaron really approaches God. He really establishes forgiveness of sins, both for himself and for the people.
The sacrificial system laid out in Leviticus is based on a series of very memorable acts which show God's condemnation of sin as well as the application of a substitute to the human sinner. The animal in the sin offering is killed. Sin brings death. The blood of the animal is put on the altar and on the person making the offering. The animal is destroyed. The sinner bringing the offering lives. It's all very concrete. It's unmistakable. You don't do something like that and forget it.
Likewise, Jesus' offering himself once for the sins of all the people, Jesus' true death on our behalf, Jesus' true bodily resurrection - this is something that is unforgettable. Yet sadly we, as doubtless did the Israelites, can tend to take it for granted. May the Lord remind us of his genuine work on our behalf, his becoming the offering for sin, his approach to the altar of God, bringing himself as the sacrificial animal, applying the blood to God's altar and to us who believe.