Is it valid to stipulate that a sheep must be one that yields milk (labun)?

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The stipulation that a sheep must be one that yields milk is valid. This is supported by Al-Shafi'i. The basis for validity is that this is a desired attribute verifiable in living animals, and it accounts for a portion of the price, making its stipulation valid, analogous to stipulating craftsmanship in a female slave. Milk itself is not sold separately due to ambiguity (jahalah), which voids a sale if it were independent. However, if purchased along with the ewe without a specific condition, the sale is valid, similar to the validity of selling wall foundations or date pits sold alongside the main commodity, even if they cannot be sold independently.