The 241st mitzvah is that we are commanded to follow the laws regarding damage caused by fire.
The source of this commandment is G‑d's statement1 (exalted be He), "If fire gets out of control and spreads through weeds [...the one who started the fire must pay for the damage.]"
The details of this mitzvah are explained in the 2nd and 6th chapters of tractate Bava Kama.
