There was a process to declare a person clean from leprosy, and part of the process was this,
“The priest shall take some of the blood of the trespass offering, and the priest shall put it on the tip of the right ear of him who is to be cleansed, on the thumb of his right hand, and on the big toe of his right foot” (Leviticus 14:14).
Then the priest used oil to sprinkle before the Lord seven times (Leviticus 14:15-16), and with the rest of the oil the priest put it on the same places on the former leper that the priest put the blood, and then with some of the oil, the priest put it on the head of the one being cleansed, and by this atonement was made (Leviticus 14:17-18).
The priest finished the process with offerings (Leviticus 14:19-20).
We are tempted to think that this was so complicated, yet, when we are ill or have serious disease, we go to the doctor and it can be just as complicated, or perhaps more complicated.
Moreover, to cleanse us from our sin, the Lord revealed all the contents of the Bible, and then Jesus died to cleanse us from our sin that we might present ourselves to God!