Al-Shāfiʿī, however, permits their sale only after the plants have been uprooted, classing the matter as the sale of an unseen commodity.
From the same category is the sale of walnuts, almonds, or broad beans while still in their shells: Mālik allows it, whereas al-Shāfiʿī prohibits it.
The reason for their disagreement is whether the element of uncertainty (gharar) involved is of the sort that invalidates a transaction or one that does not. They are agreed that gharar is of two kinds, and that the harmless kind is either slight, necessitated by need, or combines the two.
Likewise, they differed over the sale of fish in a pool or reservoir. Abū Ḥanīfah deemed it permissible, while Mālik—and, as far as I can tell, al-Shāfiʿī, which accords with his legal principles—deemed it impermissible.
The same applies to the sale of a runaway slave. Some jurists allowed it outright, others—among them al-Shāfiʿī—rejected it outright. Mālik said that it is valid provided the slave’s description and whereabouts are known to both seller and buyer; he appears further to stipulate that the fact of the slave’s flight be acknowledged and that the price be reduced accordingly—meaning that the seller does not receive payment until the buyer has taken possession. At the moment of contract, the deal vacillates between a sale and a loan; on this basis Mālik disallows cash payment in a muwāḍaʿah sale, in the sale of an untrusted absentee article, and in transactions of the same type.
Among those who sanctioned the sale of a runaway slave or a stray camel was ʿUthmān al-Battī.
Al-Shāfiʿī’s proof is the ḥadīth related by Shahr ibn Ḥawshab from Abū Saʿīd al-Khudrī:

“The Messenger of God—peace and blessings be upon him—forbade the purchase of a runaway slave, the purchase of what is in the wombs of livestock until they give birth, the purchase of what is in their udders, and the purchase of spoils of war until they have been divided.”

Mālik nevertheless allows the sale of the milk of a flock of sheep for a specified number of days when the usual amount milked from them is commonly known, but he does not allow this in the case of a single ewe. All the other jurists say that such a sale is valid only when the milk is measured with a known measure after milking.
From the same chapter Mālik forbids the sale of meat while still in its hide.
Also related is the sale of a sick animal: Mālik permits it unless the animal is judged beyond recovery, whereas al-Shāfiʿī and Abū Ḥanīfah forbid it—and a second report attributes that view to Mālik as well.
Likewise, with regard to mining earth and the sweepings of goldsmiths: Mālik allows the sale of ore-bearing earth for cash of a different kind or for other goods, but he disallows the sale of goldsmiths’ sweepings. Al-Shāfiʿī bans both, while others allow both; this last view is held by al-Ḥasan al-Baṣrī.
These are the sales over which the jurists disagree, most of the differences arising from lack of clarity concerning the manner in which the goods are obtained.
As for quantity, they unanimously agree that nothing sold by measure, by weight, by number, or by surface area may be sold unless its amount is known to both seller and purchaser. They likewise concur that knowledge obtained through a recognised measure or a recognised scale affects the validity of the contract. Conversely, whenever the measure or weight is unknown to both parties for any commodity ordinarily sold by measure, weight, count, or gauge, the sale is invalid. As for determining quantity by mere estimation—what they call a lump-sum sale (jazāf)—it is permissible in some cases and forbidden in others.