The Literal Commandment
You shall charge the sons of Israel, that they bring you clear oil of beaten olives for the light, to make a lamp burn continually. In the tent of meeting, outside the veil which is before the testimony, Aaron and his sons shall keep it in order from evening to morning before the LORD; it shall be a perpetual statute throughout their generations for the sons of Israel. (Exodus 27:20-21)
The literal commandment is to keep the lamp (the menorah) lit continually.
Messiah Says
Messiah implicitly affirmed this commandment when He spoke about the Law:
"Do not think that I came to abolish the Law or the Prophets; I did not come to abolish but to fulfill. For truly I say to you, until heaven and earth pass away, not the smallest letter or stroke shall pass from the Law until all is accomplished. Whoever then annuls one of the least of these commandments, and teaches others to do the same, shall be called least in the kingdom of heaven; but whoever keeps and teaches them, he shall be called great in the kingdom of heaven. (Matthew 5:17-19)
Pictures of Messiah
The menorah pictures Messiah: He is the light of the world (John 8:12).
Gold symbolizes righteousness and holiness. Just as the menorah is made entirely of solid gold so too Messiah was entirely righteous and holy.
The center branch of the seven-branched menorah was called the shamash which means "the helper". Messiah said that after His departure the Father would send the "Helper" (John 14:26) and indeed the Holy Spirit came upon the believers at Pentecost.
Just as the menorah has "tongues of fire" above each of the branches, "tongues of fire" of the Holy Spirit came upon the believers at Pentecost (Acts 2:3).
How Messiah Fulfilled
Messiah fulfilled this commandment by not performing it since it was given explicitly to the Levitical priests and He was not from the tribe of Levi.
Traditional Observance
Traditional observance of this commandment is found in the Temple observance. Absent the Temple a light is kept perpetually lit in synagogues throughout the world (whether oil lamps, gas lamps, or electric lights).
In synagogues a perpetual light is maintained in a lamp which consists generally of a glass vessel containing a wick burning in olive-oil; this is held in an ornamental metal receptacle suspended from the ceiling in front of the "Holy Ark," or "Aron ha-Ḳodesh," just as the candlestick ("menorah") in the Tabernacle and Temple had its place before the Ark of the Covenant.
The institution of the perpetual light descended from the Temple (comp. Ex 27:20; Lev 24:2) to the Synagogue as the "lesser Temple" ("miḳdash me'aṭ"; Meg. 29a). The perpetual light in the Temple, which is mentioned by classical writers (pseudo-Hecatæus, in Josephus, "Contra Ap." i. 22; Diodorus Siculus, xxxiv. 1), is usually referred to in the Talmud as the "western light" ("ner ha-ma'arabi"), it being the lamp upon the central shaft of the candlestick. The general tradition is that this lamp was never allowed to go out, while the other six lamps burned only during the night (Tamid vi. 1; Men. 86b, 98b; comp. "Yad," Bet ha-Beḥirah, iii. 1-11, and Temidin, iii. 10-18); according to Josephus, "Ant." iii. 8, § 3, three lights burned day and night in the Temple; and, again, Tamid iii. 9 would imply a tradition of two lights burning perpetually. The lighting of the perpetual lamp and the placing of the scrolls of the Law in the Ark are the principal ceremonies in the dedication of a synagogue.1
Other Notes
Absent the Temple and the menorah we are unable to literally fulfill this commandment today.
<><