What is the ruling on exchanging countable items that do not vary significantly in size, such as walnuts or eggs?
Chapter on Guaranteed Salaf (Advance Payment) for a Specified Term
Al-Mughni
Book of Sales
Primary text
The transaction for countable items that do not vary significantly in size, such as walnuts and eggs, is valid based on count. This is the position held by Abu Hanifa and Al-Awza'i. The justification rests on the premise that the variation is slight, and this variation is resolved by stipulating whether the items are large, small, or medium. Any minor remaining variation is overlooked, analogous to the pardonable variation found in measured (by volume or weight) commodities. This contrasts with items like melons, which are not counted.
Supporting text
Al-Shafi'i maintains that such items must be exchanged by measure (volume or weight) and that exchanging them by count is invalid because counting leads to variation and difference, similar to melons.