Is dough or similar substances that have become impure capable of purification?
Chapter on what purification is achieved with regarding water
Al-Mughni
Book of Purification
Primary text
Dough and similar items that become impure cannot be purified because washing them is impossible. Similarly, if sesame seeds or other grains are soaked in impure water until they swell and absorb it, they do not become purified. Regarding sesame seeds soaked in a cistern where a rat died, none of the product is to be used, even if washed repeatedly, because they have absorbed the impure water. Ahmad ruled that such items (dough, sesame) may be fed to water camels (Nawaadih) but not to animals whose meat is consumed soon. Mujahid, 'Ata', ath-Thawri, and Abu 'Ubayd permitted feeding them to chickens. Malik and ash-Shafi'i permitted feeding them to beasts of burden.
Supporting text
Ibn al-Mundhir prohibited feeding them anything, citing the Hadith where the Prophet, peace be upon him, forbade using the fat of a carcass for various purposes, stating it is forbidden. The justification for permitting feeding them to certain animals rests on the narration from Ibn 'Umar that the Prophet, peace be upon him, ordered dough made from water of the wells of the oppressors to be fed to the water camels. Furthermore, the prohibition on carcass fat is distinguished because its use involves transferring the impurity (like greasing leather), whereas the impurity of the soaked items does not transfer through consumption.