Exodus 28:43 And they shall be upon Aaron, and upon his sons, when they come in unto the tabernacle of the congregation, or when they come near unto the altar to minister in the holy place; that they bear not iniquity, and die: it shall be a statute for ever unto him and his seed after him.
God is gracious and kind. He is loving. Serving Him is fun and a blessing. But you can never take serving God lightly. It is not a game. It is not something we play at.
They were privileged and honored to serve God and lead the worship. But they should never forget that He is indeed God. He is all powerful. He is not to be trifled with. He is all powerful.
We do not deserve to be in His presence. We did not create God but rather He created us!
Getting to stand before Him and in His presence is a gift offered to us by His grace. He is God.