Exodus 27:20-21 New King James Version (NKJV)
The Care of the Lampstand
20 “And you shall command the children of Israel that they bring you pure oil of pressed olives for the light, to cause the lamp to [a]burn continually. 21 In the tabernacle of meeting, outside the veil which is before the Testimony, Aaron and his sons shall tend it from evening until morning before the Lord. It shall be a statute forever to their generations on behalf of the children of Israel.