Exodus 30:19-21

For Aaron and his sons shall wash their hands and their feet thereat: When they go into the tabernacle of the congregation, they shall wash with water, that they die not; or when they come near to the altar to minister, to burn offering made by fire unto the LORD: So they shall wash their hands and their feet, that they die not: and it shall be a statute for ever to them, {even} to him and to his seed throughout their generations.