Leviticus 10

Two of Aaron's sons disobey God, and they may have tried participating in priestly duties under the influence of alcohol. The penalty was swift, and complete.

Aaron couldn't publicly mourn, and was the instructed not to drink, and that a priest's role would be to tell the people how to live more holy, how to avoid what wasn't clean.

Sin didn't end the priesthood, nor the priestly duties. At the end of the chapter we see grace for sins that weren't done on purpose. Aaron and his sons were forgiven.