Exodus 27:20-21

CLV(i) 20 As for you, you shall instruct the sons of Israel that they shall take to you pure olive oil, pounded, for the luminary, to kindle the lamp regularly. 21 In the tent of appointment, outside of the curtain which shall be over the testimony, Aaron and his sons shall arrange it from evening until morning before Yahweh. It shall be an eonian statute throughout their generations, for the sons of Israel.