Exodus 30:17-21

Then the LORD said to Moses, “You shall also make a basin of bronze, with a base of bronze, for washing. You shall put it [outside in the court] between the Tent of Meeting and the altar [of burnt offering], and you shall put water in it. Aaron and his sons shall wash their hands and their feet. When 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]. [John 13:6-8] They 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.”