The neir tamid that hangs above the ark in every shul and never goes out reminds us of three flames that burned in the Beis HaMikdash. One was the light of the menorah which was lit every single day and burned from the evening until the morning. Some opinions say that the western lamp of the menorah burned continually (Shemos 27:20–21). The neir tamid also reminds us of three fires that burned on the Mizbeiyach: the large fire upon which offerings were burned the fire that was used to light the ketores (incense) and the smaller fire from which burning wood was taken for the large fire (Vayikra 6:2 and 5). The neir tamid also reminds us of the golden Mizbeiyach which was used to burn incense every morning and evening.

What a lot of beautiful things to remember when we see that small electric flame flickering!