by volume, whereas a weighed commodity is assessed according to its heaviness or lightness. Thus, wheat is a measured commodity; if it is sold in exchange for wheat, equality must be determined by volume. If it is sold for the same type by weight, the sale is invalid, and this is not regarded as equality—even in commodities for which weight and volume yield the same result, such as oils and milk. They fall under the category of measured commodities, because every liquid commodity subject to ribā is measured by volume. Milk, therefore, is among measured commodities. Although its weight and volume do not differ, if it is sold by weight, then according to the author’s view the sale is invalid. Thus, if I sell milk for milk of the same type by weight, it is invalid, even though they would have been equal had they been measured by volume.
Shaykh al-Islam, may Allah have mercy on him, held that if measurement by volume and by weight yield the same result, there is no harm in selling a measured commodity for the same type either by volume or by weight, because the Prophet, peace and blessings be upon him, said: “Like for like.” (1) In this case, equivalence is achieved. But where volume and weight yield differing results, a measured commodity must be sold by volume, and a weighed commodity by weight.
The author’s statement, “Nor may a weighed commodity be sold for the same type except by weight,” applies, for example, to meat. If someone sells the meat of one sheep for the meat of another sheep, this is a weighed commodity. If he wishes to cut the meat into small pieces, place them in a container, and sell it for the same type by volume, this is invalid, because meat is assessed by weight.
Some scholars said that a measured commodity may be sold by weight, with equality determined by weight, but not the reverse; that is, a weighed commodity may not be sold by volume. However, the cautious position is that a measured commodity should be sold only by volume, and a weighed commodity should not be sold for the same type except