The blood on Aarons ear.
And he slew it: and Moses took of the blood of it, and put it on the tip of Aaron’s right ear, and upon the thumb of his right hand, and upon the big toe of his right foot.
In this scripture, Aaron and his sons were of the tribe of Levi, which was the priestly tribe, and were responsible for the blood sacrifice for the sins of the people.
When Moses took the blood of the ram, and put it on Aaron’s ear, it symbolized that he would hear the voice of God, while the blood tipped thumb symbolized that the hand was essential for the service of the Lord. The blood tipped toe was essential for the walk before God. After Moses sprinkled Aaron in this way, he then sprinkled his son’s in the same way.
This scripture is a reminder of the blood being offered as a sacrifice for our sins. All things were cleansed with blood, and without the shedding of blood, there was no forgiveness of sins. In the Old Testament, the blood of bulls, rams, etc. were a temporary sacrifice for sin. In the New Testament, Jesus Christ shed His blood on the cross once for all.