Siman 255

As has been explained, just as the sages were concerned regarding foods placed near darkness, that one must decree lest he rake the coals, so too they decreed regarding those who make a wood bonfire near darkness, that they may not benefit from it unless they lit it while it was still day in a manner that it no longer requires assistance for the lighting, so that it burns on its own. Therefore, one may not make a bonfire of wood near darkness until the fire takes hold in them in a manner that the flame rises on its own without the assistance of other wood. And if it is a single log—the fire must take hold in the majority of its thickness on the inside, and in the majority of its circumference on the outside. And if it was not lit to this extent—it is forbidden to use it on Shabbat to sit near it or to use its light, as a decree lest he rake in order to burn it well, and he will rake and move the wood so that the flame rises. And even if it was afterwards completely lit—it is forbidden, just as with the foods that we forbade even after their cooking was finished, and such is the law here. But when it was lit to the required measure before night—he may use it as much as he desires, whether to warm himself before it on Shabbat or to use its light, whether it is on the ground or whether it is on a lampstand, and even from materials that one may not make into wicks for Shabbat as will be explained in siman 264, for there we decree lest he tilt, since it is merely a lamp. But with a bonfire which has much light—"lest he tilt" is not applicable, and see in siman 275.

There is one who says that in any case, when one sits near a bonfire, he should not sit close to the ends of the firebrands which are called "haloveska," for there is a concern that he might touch them to turn them over so that they burn well, as is the way of people to do. (Taz in siman 275, subsection 6). And there is one who disagrees regarding this, for specifically regarding study which requires great concentration, in that case they decreed there that due to the preoccupation of his study he might forget and act. But where it is not a place of concentration, rather to sit and warm oneself, we have not found this decree (Tosefet Shabbat). And that which they forbade when the flame does not yet rise on its own, this is for the reason that he might fear lest it be extinguished entirely; but as long as this concern is removed, they were no longer concerned, and so it appears primary.

The Tur wrote that regarding coals, even if the fire has only caught them slightly, it is permitted because they continue to burn on their own. Thus far his words. In the Rambam this was not mentioned, and in the Mishnah at the end of the first chapter there is a dispute regarding this, for the sages did not mention this and only Rabbi Yehuda says so regarding coals, even slightly. And they questioned the Tur, for how could he rule like an individual against the many? Some have written that he holds that Rabbi Yehuda comes to explain, but it is difficult to say so, for this is only when he says "In what case are these words said" or "When." (See Bach) But the truth is that it is proven so in the Yerushalmi, that the halacha is like Rabbi Yehuda, see there.

A bonfire of pitch and of sulfur (it seems to me that this refers to wood coated in pitch and sulfur, and examine this closely) and of straw and stubble, even if the fire has only caught in them any small amount—it is permitted, for they continue to burn on their own; and likewise a bonfire of thin reeds and of date pits when they are scattered. But if the reeds are bound and the pits are in a basket—they are not so easy to ignite, and it is required that the flame rise of its own accord as with all other wood. This follows the version of the Rif and the Rambam in the Gemara (end of the first chapter), but the version of the Rosh and the Tur is the opposite: that when they are scattered—it is required that the flame rise of its own accord, and when they are gathered—even if it has only caught any small amount. And the Tur wrote in siman 502: "A bonfire made of thin wood—it is permitted to remove from them as long as the fire has not caught in them," see there, and the same law applies on Shabbat in such cases if the wood is not muktzeh. (And likewise for one who arranges wood and ignites a long rope from a distance until it reaches the wood, as long as it has not reached the wood—it is permitted to take from them on Yom Tov or on Shabbat, when the wood is not muktzeh.)