13. When the buyer learns that the animal was subjected to taṣriya and returns it after milking, he must send back with it one ṣāʿ of dates in lieu of the milk—whether the animal is sheep, camel, or cow, and whether the milk was little or much. The Lawgiver fixed the compensation at this precise measure, neither more nor less, to pre-empt argument and dispute that would arise if the amount were left to the parties, each claiming the milk was greater, smaller, or mixed with milk that formed in the udder later. Using dates is preferable, for both dates and milk were staple foods at that time and both are measured by volume. These dates correspond to the milk that was purchased while still in the udder; as for any milk produced afterwards, nothing is returned, because “the yield goes to the one who bears liability” (al-kharāj bi-l-ḍamān).

14. The prohibition of najsh: this is when someone who has no intention of buying the item raises its price, either to benefit the seller or to harm the prospective buyer—and he may even aim to injure them both. It is unlawful, for every prohibition implies prohibition. If he colludes with the seller in this practice, the two share the sin, and it establishes the buyer’s right of option in the sale.

Disagreement among the scholars:
• The majority maintain that the purchase made by one who intercepts incoming caravans (talqī al-rukbān) is valid; some even report consensus on the point. Their evidence is the ḥadith recorded by Muslim and others: “Do not meet merchandise on the way; whoever does and buys from it, then when its owner reaches the market he has the choice.” The prohibition in the ḥadith does not relate to the contract itself, or to any of its pillars or conditions, but is meant to prevent harm to the caravanners; hence it does not vitiate the sale, for the harm can be remedied.
• They disagreed, however, about the right of option. Al-Shāfiʿī and Aḥmad hold that it is established whenever the seller suffers a loss exceeding customary commercial practice. Their proof is the foregoing ḥadith, and because the harm inflicted on the seller cannot be rectified except through this option. The Ḥanafīs deny that any option exists, but the first view is the sounder one.
• They also differed over the validity of a sale concluded over another’s sale. Imām Aḥmad, in his well-known position, and the Ẓāhirīs considered the sale invalid and non-binding, because it is prohibited and a prohibition entails invalidity. The other three Imams, however, deemed the sale valid, for the prohibition does not pertain to the essence of the contract but to an extraneous matter.