Exodus 27:20-21 ESV
“You shall command the people of Israel that they bring to you pure beaten olive oil for the light, that a lamp may regularly be set up to burn. In the tent of meeting, outside the veil that is before the testimony, Aaron and his sons shall tend it from evening to morning before the LORD. It shall be a statute forever to be observed throughout their generations by the people of Israel.
ESV: English Standard Version 2016