Speak to Aaron, saying: ‘No man of your descendants in succeeding generations, who has any defect, may approach to offer the bread of his God.
LEVITICUS 21:17
God has brought His people, the Israelites out of cruel bondage and slavery in Egypt. Having seen His power at work on their behalf and proclaiming Him as their God however, they don’t believe in Him so God brings them into the wilderness to separate them from the nations around them whose ways they desire to follow, ways fuelled by violent abuses of power and the sacrifice of their own children to gods of their own making.
In order to distinguish Himself from their gods and His ways from their ways, God gives them His law to establish the worship of Him alone as the one true God and to facilitate the care and consideration of each other. To fulfil the requirements of His law He sets apart a tribe and lineage of people to be priests to instruct the people and bring offerings of thanksgiving and the sacrifice of birds and animals in the event the people transgress His law unintentionally. The priests are given specific instructions on how to behave and how to present the offerings and as they approach God on behalf of the people, they are to be pure and without blemish as any defect would compromise an otherwise perceived perfect representation of the people in their eyes before He who is true, holy, righteous and good.
Time passes and God comes into the world as a human being to offer Himself as the sacrifice for humanity’s sin. After His death, resurrection and ascension back to heaven, He now sits as High Priest, holy, innocent, undefiled and separate from sinners who is able to save to the uttermost those who come to God through Him.
References
LEVITICUS 10:1-3, 20:22-26, 21:4,6,8,17,23, PSALM 78:8, MATTHEW 5:17, 2 CORINTHIANS 5:21, HEBREWS 7:25-8:2, 9:26, 10:22.