Is the sale of milk remaining in the udder permissible?
Chapter on Selling the Musarrah (Animal with milk retained in udder)
Al-Mughni
Book of Sales
Primary text
The sale of milk while it is still in the udder is prohibited. This position is held by Al-Shafi'i, Ishaq, and the companions of opinion (Ahl al-Ra'y). Ibn Abbas and Abu Hurayrah prohibited it. The basis for this prohibition is the report from Ibn Abbas that the Messenger of Allah, peace and blessings be upon him, forbade the sale of wool on the back or milk in the udder, narrated by Al-Khall with his chain of narration. The justification is that the object of sale is unknown in both description and quantity, resembling the sale of a fetus (haml). It is a sale of something not yet created, which is impermissible, similar to selling what a she-camel is carrying, as the customary amount varies greatly.
Supporting text
Malik reported an opinion allowing it for a known number of days, provided the milking time is known, specifically if the milk is intended for nursing an infant, analogous to the milk of a wet nurse (dhirr). Al-Hasan, Sa'id ibn Jubayr, and Muhammad ibn Muslimah permitted it.