then this is permissible, because livestock is neither measured by volume nor by weight. Hence the Prophet ﷺ would borrow against the charity camels, taking one camel for two camels, and two camels for three. (1) Accordingly, there is no ribā in livestock so long as it is alive. Once it is slaughtered, however, it becomes meat, and ribā applies to it. Thus, if it is sold for the same genus, equality is indispensable; otherwise, the sale is invalid.

The same applies to milk, meat, fat, and liver: they are distinct genera. It is not valid to sell meat for a live animal of the same genus, though it is valid if the animal is of a different genus.

His statement, “The same applies to milk”: milk comprises distinct genera according to its source. Camel milk is one genus, and cow’s milk is another. Thus, if I sell one sāʿ of camel milk for two sāʿs of cow’s milk, this is permissible because the genera differ. But if I sell one sāʿ of milk from a young cow for two sāʿs of milk from an old cow, this is not permissible, because they are of the same genus.

His statement, “meat, fat, and liver are distinct genera”: the author now shifts from considering each animal independently as a genus to considering the different parts within a single animal as separate genera. An animal contains various kinds of flesh: meat, fat, liver, heart, rump fat, spleen, lung, hoof, eye, and head. Each of these is a distinct genus. Accordingly, one may sell you one ratl of liver for two ratls of lung, even if both are from sheep, because the genera differ. Likewise, I may sell one ratl of lung for two ratls of meat from the very same sheep, because the genera differ,