Exodus 30:19-21

19Aaron and his sons shall wash their hands and their feet.

20When they enter the Tent of Meeting, they shall wash with water, so that they will not die. Also, when they approach the altar to minister, to burn an offering in the fire to the Lord [they shall do the same].

21They shall wash their hands and their feet, so that they will not die; it shall be a perpetual statute for them, for Aaron and his descendants throughout their generations.”