Leviticus 24:2-4

2“Command the Israelites to bring you clear oil of pressed olives for the light so that the lamps may be kept burning continually. 3Outside the curtain that shields the ark of the covenant law in the tent of meeting, Aaron is to tend the lamps before the Lord from evening till morning, continually. This is to be a lasting ordinance for the generations to come. 4The lamps on the pure gold lampstand before the Lord must be tended continually.