Exodus 27:20-21
20“And you shall command the sons of Israel, that they bring you aclear oil of beaten olives for the 1light, to make a lamp 2burn continually. 21“In the atent of meeting, outside bthe veil which is before the testimony, cAaron and his sons shall keep it in order from evening to morning before Yahweh; it shall be a perpetual dstatute throughout their generations 1for the sons of Israel.