How do we know that cleansing is necessary for all who serve God?

The necessity of cleansing for those who serve God is illustrated through the requirements placed on the priests in the Old Testament. As stated in Exodus, if Aaron and his sons did not wash their hands and feet, they would die. This highlights the gravity of serving before a holy God and reflects the principle that spiritual cleanliness is essential for divine service. All who approach God—especially those ministering to others—must do so with an awareness of their sinfulness and an understanding of the cleansing provided by Jesus Christ's blood, which makes them fit for service and worship.