Following the Torah’s directions for the physical structure of the Mikdash (the Sanctuary), Parshat Tetzaveh sets forth the laws regarding the kohanim (priests) and certain priestly rituals to be performed in the Sanctuary. The parshah opens with a description of the Ner Tamid, discusses in great detail the priestly garments and the consecration of priests, touches briefly on the laws of daily sacrifice, and closes with the requirements for the altar of incense.
"Ner Tamid" is traditionally translated as the "eternal light." The Torah commands:
And thou shalt command the children of Israel, that they bring unto thee pure olive oil beaten for the light, to cause a lamp to burn continually. In the tent of meeting, without the veil which is before the testimony, Aaron and his sons shall set it in order, to burn from evening to morning before the Lord; it shall be a statute for ever throughout their generations on the behalf of the children of Israel.
Exodus 27:20-21. Aaron was to light the lamp at dusk, and to remove the burnt wick, replace it with a fresh wick, and fill the lamp with oil in the morning. Exodus 30:7-8.
Although the parshah does not explain the reason for this set of commandments, the focus is more on activities to keep the Ner Tamid burning than on the lamp as part of the physical building. The Rabbis recognized this emphasis by understanding the Ner Tamid as a symbol of Israel. The importance of this ritual was not just to maintain the Sanctuary, but to symbolize the connection between God and Israel.
Light – and specifically light from an olive oil lamp (or, in modern days, from candles) – remains an ever-present part of Jewish ritual. We light candles to mark the beginning and end of Shabbat. We light candles on Yom Tov and Hanukkah. We light candles during shiva and to observe yahrzeit. In every synagogue, the Ner Tamid burns over the Ark. The significance is not just in the light itself, but in the connection the light represents between us and God.