Exodus 30:18-20

18“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.

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].