As for milk for colostrum (liba'), if it is before being touched by fire, it is permissible as equivalents (tamathulan), because it is milk for milk. If it is touched by fire, it is not permissible. Al-Qadi mentioned a view that it is permissible, but it is not correct, because fire has coagulated the parts of one of them and taken away some of its moisture, so it is not permissible to sell it for that which has not been touched by fire, like bread for dough, or fried for raw. This is the school of al-Shafi'i. As for selling a type of milk derivative for its own type, that which contains a mixture other than milk, such as kishk, kamakh, and the like, it is not permissible [to sell it] for its own type or for another; because it is mixed with other things, so it is like the issue of the mudd of 'ajwa dates. As for that which does not contain other things, or contains something else, provided that the other thing is for its benefit, it is permissible to sell each type of it for part of itself if they are equal in dryness and moisture. Thus, one sells buttermilk for buttermilk, colostrum for colostrum, cheese for cheese, whey (masl) for whey, dried yogurt (aqit) for dried yogurt, butter for butter, and clarified butter (samn) for clarified butter, while equal. Equality between dried yogurt (aqit) for dried yogurt is considered by measure (kayl); because it was estimated by the sa' in the zakat al-fitr, and it resembles the measured items, and likewise for whey and buttermilk. Bread is sold for bread by weight, because it is a weighted item and cannot be measured, so it resembles bread. Likewise for butter and clarified butter. It is inferred that clarified butter may be sold by measure. A dry item of these shall not be sold for a moist one, just as moist dates are not sold for dry dates. The statement of al-Khiraqi may imply that a moist item of these shall not be sold for a moist one [as in the case of meat]. As for selling what has been extracted from milk for another type, such as butter, clarified butter, and buttermilk, the apparent position of the school is that it is permissible to sell butter and clarified butter for buttermilk, whether as equivalents or with a surplus; because they are two different genera, and this is because they are two things from one origin, resembling meat for fat. Among those who permitted the sale of butter for buttermilk are al-Thawri, al-Shafi'i, and Ishaq. This is because the milk contained in the butter is not intended, and it is minimal, so it resembles