First subsidiary issue
All the jurists concur that when the produce belongs to one and the same kind of grain or fruit, its superior and inferior portions are aggregated, and the Zakāt is levied on the entire amount in proportion to the quantity of each—good and poor. If the fruit itself contains several qualities, the collector takes from the middle grade.
They differed, however, over whether different legumes may be combined to complete the niṣāb, and over combining wheat, barley, and sult. Mālik maintained that all legumes constitute a single kind, and that wheat, barley, and sult likewise count as one. Al-Shāfiʿī, Abū Ḥanīfa, Aḥmad, and a number of others held that legumes comprise many distinct kinds according to their various names, so nothing of one kind may be added to another in calculating the niṣāb. The same, in their view, applies to barley, sult, and wheat: they are three separate kinds, none of which may be joined to another to complete the niṣāb.
The root of the disagreement is whether sameness of kind is determined by identical uses or by identical names. Whoever gives weight to names says: whenever the names differ, the kinds are many. Whoever gives weight to uses says: whenever the uses coincide, the produce is a single kind even if the names differ. Each side tries to ground its principle by surveying the Sharīʿah—one citing cases in which the Law considers names, the other citing cases in which it considers benefits. It would appear that, in the matter of Zakāt, the Sharīʿah bears witness to names more than to benefits, though both considerations are found in the Law. Allah knows best.
Second subsidiary issue—determining the niṣāb by kharṣ (ocular estimation) rather than by actual measurement
The majority of scholars permit kharṣ for date-palms and grapes once they show signs of ripening, out of necessity, so that the owners may be left free to consume the produce fresh. Dāʾūd said that kharṣ is lawful only for date-palms. Abū Ḥanīfa and his two companions declared kharṣ invalid; the owner, they say, must pay one-tenth of whatever actually comes into his possession, whether the estimation proves higher or lower.
Their dispute over kharṣ stems from a clash between general legal principles and the transmitted report on the matter. As for the report—on which the majority rely—it is the ḥadīth that relates:
“The Messenger of Allah—peace and blessings be upon him—used to send ʿAbd Allāh ibn Rawāḥah and others to Khaybar, and they would estimate the yield of its date-palms.”