Rambam - 1 Chapter a Day

The remnants of a larger oven are four handbreadths. The remnants of a small oven are its larger portion.

What is implied? If a large oven is broken, as long as four handbreadths remain, it is susceptible to impurity. And if a small oven is broken, as long as its larger portion remains, it is susceptible to impurity. Similarly, if a large oven contracted impurity and it was smashed to the extent that less than four handbreaths remain, it is pure. A small oven becomes pure when less than its larger portion remains. If more than four handbreadths of a large oven remain or the larger portion of a small oven, it remains impure.

The remnants of a range with two openings are three fingerbreadths. For a range with one opening: If it was made for baking, the measure is the same as that of an oven. If it was made for cooking, the measure is the same as that of a range.

How can the owner restore the purity of an oven that contracted impurity that he does not want to destroy? It should be divided into three portions and the coating removed from the shards so that each shard is standing on the earth without a coating of clay.

If he divided it in two, leaving one large portion and one smaller portion, the larger portion is impure and the smaller portion is pure. If they are both of equal size, they are both impure, because it is impossible to make an exact determination which is larger. When, by contrast, an earthenware tabletop with a wall was divided in two equal portions, they are both pure. If one was larger and one smaller, the larger one is impure.

When an impure oven is divided into three portions and one is as large as the other two, the large portion is impure.

The following laws apply if such an oven was cut into circular portions, widthwise. If the height of every ring was less than four handbreadths, it is pure. If, afterwards, one arranges the rings one on top of the other and coats them with clay, making them into an oven as they were before, it is as if he made a different oven. It is susceptible to impurity only from the time it was reconstructed, provided it was heated to the extent that doughnuts could be baked in it after it was coated with clay.

If one separated the clay coating from the substance of the oven itself and placed sand or pebbles between the rings and the coating, it never becomes susceptible to impurity. Concerning this type of oven, it was said: A woman who is a nidah and one who is pure may both bake inside of it and everything is pure.

If it has one ring that is four handbreadths high and that ring contracts impurity through physical contact with a source of impurity and not from the presence of impurity within its inner space, the remainder of the rings are pure.

The following rules apply when an oven comes cut in pieces from the craftsman's shop and one makes supports for it so that they will be joined together as a single entity. If one placed them there while it was pure and it contracted impurity, when one removes the supports, it regains purity. Even after he returns them, it remains pure. If one coated the portions of the oven with clay, they become susceptible to impurity from that time onward. It is not necessary to heat the oven, because it was already heated the first time it was assembled.

When an oven was cut into rings, sand placed between each ring, and the entire structure coated with clay from the outside, it is susceptible to ritual impurity.

A pit used by Arabs - i.e., one digs in the earth, coats the pit with clay, and bakes in it - is governed by the following rules: If the clay could stand independently, it is susceptible to ritual impurity. If not, it is pure.

When one brings earthenware shards and sticks them together and forms an oven from them, making a coating for them from the inside and from the outside, after he heats it, it becomes susceptible to impurity, even though none of the shards is of the size required.

When one removed the base of a large barrel and made it into an oven, coating its exterior with clay, it is pure even though its walls are capable of containing the required amount. The rationale is that once an earthenware container is classified as not being susceptible to impurity, it never becomes susceptible again unless one makes it into an oven and coats it on the inside and on the outside.

When there is an oven with cracks for which a coating was made for each of the pieces, but the place of the cracks was left open, it is not susceptible to impurity. If clay, lime, or gypsum were placed on the cracks, it is susceptible to impurity. If one patched it with a paste made from ground earthenware and water, tar, sulfur, beeswax, yeast, dough, or animal turds, it is pure. This is the general principle: An entity from which an oven is not usually made is not considered as being sufficient to patch the cracks.

When the crack in an oven is positioned in a corner, even though one smeared clay at the sides, it is pure.

When a shelf outside an oven was placed in a corner in order to bake with it, it is pure. If it comprises the majority of the oven, it is susceptible to impurity.

The following rules apply when a person filled half of an oven with earth. If the oven contracted impurity from its inner space alone, only the portion above the earth contracts impurity. If it contracted impurity from contact with a source of impurity and the impurity touched its inside, the entire oven contracts impurity, even the portion below the earth.

The term kirah refers to a range with a place for two pots to rest; the term kopach refers to a range with a place for one pot to rest. Therefore if a kirah is divided lengthwise, it is pure. If it is split across its width, it is still susceptible to impurity. When, by contrast, a kopach is split, it is pure whether it is split lengthwise or widthwise.

The following rules apply when there is an opening in the upper surface of the base used by homeowners placed below a range. If the opening is less than three handbreadths deep, the range is susceptible to impurity, because if the kindling fuel is less than three handbreadths from the bottom of the range, a pot placed above will cook. If the opening is three handbreadths or more deep, it is not susceptible to impurity, because the fire will be too far from the pot and it will not cook.

If one places a stone or a rock over the opening, the range is still pure. If one coated the stone with clay, it becomes the base of the range and the range is susceptible to impurity in the future.