Exodus 27:20-21 “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.
Leviticus 24:2-4 “Command the people of Israel to bring you pure oil from beaten olives for the lamp, that a light may be kept burning regularly. Outside the veil of the testimony, in the tent of meeting, Aaron shall arrange it from evening to morning before the LORD regularly. It shall be a statute forever throughout your generations.
And thou shall command the children of Israel,…. Here begins a new section of the law; an account being given of the tabernacle, and its parts, and the furniture thereof, next the several parts of service done in it are observed; and the account begins with that of the candlestick in the holy place, in order to which Moses is directed to command the people of Israel, whose business it was to provide for it: that they bring thee pure oil olive beaten for the light; for the light of the candlestick, to light up the several lamps in the several branches of it; and the oil to be brought and used there was not any sort of oil, as what is got out of fishes, as train oil, or out of nuts, as oil of almonds, but what comes from the olive tree; and this must be pure and free from lees and dregs, and must be beaten with a pestle in a mortar, and not ground in a mill, that so it might be quite clear; for being bruised and beaten, only the pulp or flesh of the olive was broken, but being ground in a mill, the stones were broken and ground, and so the oil not so pure.Jarchi and Ben Melech, from their Rabbins, observe, that after the first drop was pressed out, they put them into mills and grind them; but then, though the oil was fit for offerings, it was not fit for the light of the candlestick. Ben Gersom says, they put the olives bruised into a basket, and the oil dropped from them without pressing at all; and this was the choicest and most excellent for the light. The quantity to be brought is not fixed; but the measure fixed by the wise men of Israel, as Jarchi says, was half a log, that is, for every lamp; and this was the measure for the longest nights, the nights of the month Tebet, and so the same for all other nights: to cause the lamp to burn always night and day, continually, as it was proper it should, that the house of God might not be at any time in darkness; as it would otherwise be, since there were no windows in it; and his servants minister in it in the dark, even in the daytime, at the altar of incense, and at the shewbread table, which is not reasonable to suppose; and though there are some passages of Scripture which seem to intimate as though the lamps only burnt till the morning, and then went out, and were lighted every evening; this difficulty may be solved, and the matter reconciled by what Josephus (l) relates, who must be an eyewitness of it, that three of the lamps burned before the Lord in the daytime, and the rest were lighted at the evening. (Gill)