Leviticus 6:6 "Fire shall be kept burning continuously upon the altar; it shall not go out"

It was very late one night, when Shimi and his father passed by the neighborhood synagogue.

Inside, Shimi saw a faint, reddish light glowing.

"Daddy, why is there a light on inside?" Shimi asked. "Nobody is in the synagogue, and even if someone were there, that would not be enough light to see by."

"That's a special light," his father answered. "It's not there to give light, Shimi."

"You see, in the Beit HaMikdash, the priests were commanded to light a fire on the altar every morning and evening. Even though G‑d sent down heavenly fire to consume the sacrifices, he wanted us to light a fire every day."

"That special light in the Synagogue is called a 'Ner Tamid', which means 'an everlasting light.' It reminds us that a synagogue is like a tiny Beit HaMikdash and that our prayers, which replace sacrifices, are always welcome, because like sacrifices they bring us closer to HaShem."

This Negative Mitzvah prohibits us from extinguishing the fire on the Altar, (see Positive Mitzvah 29.)