Leviticus 21 is about the priests’ requirement to stay holy. They are given warnings and requirements for how they must keep holy and undefiled.
If the priest became defiled, then they could not enter the sanctuary and make the offering. That would be disastrous for God’s people. The priests’ keeping themselves holy was a life and death matter.
They aren’t to defile themselves with a dead person. They aren’t to defile themselves for their parents.
This is very reminiscent of Jesus telling would-be disciples to let the dead bury their own dead and that if they turned back even to say goodbye to their father, they were not worthy of being disciples. Once you are following Jesus, you cannot look back.
We are called to be holy, set apart for God. That means separated from the world. That means we’re His alone. We’re not holy if we have torn allegiances. There has to be one that’s the one that matters.
No one with any blemish can be a priest. They can’t even approach the altar if they have a scab. They can’t work as a priest with a broken foot, so forget about it if you are permanently lame.
Jesus, of course, flipped this all on its head. Everyone could come to Him and be made whole. They were all acceptable.
Now, all believers are called priests. And we must approach the secret place with holiness. We come to the cross in our sin. We come to the altar in our holy array. We’re to be in God’s presence blameless.
It’s the job of Jesus to present us blameless before the Father. He cleanses us and puts His Spirit in us and dresses us in His robes of righteousness.
If we’re to present ourselves as living sacrifices on the altar, then we must be a holy sacrifice. We must give ourselves to God alone. We can’t place the same sacrifice on altars to different gods. We must offer ourselves to Him alone.