Rabbi Zerachiah ben Isaac Ha-Levi Gerondi (Hebrew: רבינו זרחיה הלוי), "the Baal Ha-Maor" (author of the book Ha-Maor), went as far as to write that "he who does not eat warm food (on Shabbos) should be checked out to see if he is not a Min (a heretic)". The reasoning behind such austerity is that the Karaites interpreted the Torah verse, "You shall not (Heb: "bi‘er" the pi‘el form of "ba‘ar") a fire in any of your dwellings on the day of Shabbat" to indicate that fire should not be left burning in a Jewish home on Shabbat, regardless of whether it was lit prior to, or during the Sabbath. In Rabbinic Judaism however, the "qal" verb form "ba‘ar" is understood to mean "burn", whereas the "pi`el" form (present here) is understood to be not intensive as usual but causative. (The rule being that the pi'el of a stative verb will be causative, instead of the usual hif'il.) Hence "bi`er" means "kindle", which is why Rabbinic Judaism prohibits only "starting" a fire on Shabbat.