And the 81st prohibition is that we are forbidden from extinguishing the fire on the altar.

The source of this commandment is G‑d's statement1 (exalted be He), "Fire shall be kept burning on the altar continually; it must not go out."

The Sifra2 says, "The phrase 'it must not go out,' teaches that one who extinguishes [the fire] transgresses a prohibition." One who transgresses this prohibition and extinguishes even a single coal from the altar is punished by lashes.

The details of this mitzvah have been explained in the 10th chapter of tractate Zevachim.3