The root of their disagreement over whether zakāh is or is not incumbent upon such a person goes back to their differing conceptions of the legal nature of zakāh itself. Is it an act of worship, like the prayer and the fast, or is it a fixed financial right that the poor hold over the wealth of the rich?

Whoever views it as an act of worship makes the condition of legal adulthood a prerequisite; whoever regards it as an obligatory right due to the poor and needy from the property of the affluent does not consider adulthood at all.

As for those who distinguish between produce that the land yields and property that the land does not yield, or between assets that are hidden and those that are openly apparent, I know of no sound basis for their view in our time.

Concerning non-Muslim subjects (ahl al-dhimmah), the majority maintain that no zakāh is levied on any of them, apart from a report stating that the zakāh rate was doubled for the Christian tribe of Banū Taghlib—meaning that they were to be charged exactly what is taken from Muslims in every category. Those who adopt this position include al-Shāfiʿī, Abū Ḥanīfah, Aḥmad, and al-Thawrī. Nothing is recorded from Mālik on the matter. They relied on the fact that ʿUmar ibn al-Khaṭṭāb actually imposed such a levy on them, and they apparently treated his action as a binding precedent, although the general legal principles run counter to it.

As for slaves, scholars fall into three camps. One group holds that there is absolutely no zakāh on the wealth of a slave; this is the view of Ibn ʿUmar and Jābir among the Companions, and of Mālik, Aḥmad, and Abū ʿUbayd among the jurists. A second group maintains that the zakāh on a slave’s wealth is the responsibility of his master; such is the position of al-Shāfiʿī—as reported by Ibn al-Mundhir—along with al-Thawrī, Abū Ḥanīfah, and his colleagues. A third group obligates zakāh on the slave himself in respect of his own property; this is related from Ibn ʿUmar, and was adopted by ʿAṭāʾ, Abū Thawr, the Ẓāhirīs, and others.

The majority of those who hold that no zakāh is due on a slave’s assets likewise say there is no zakāh on the wealth of a contract-slave (mukātab) until he attains freedom. Abū Thawr, however, rules that zakāh is due on the mukātab’s property.

The reason they differ over zakāh on a slave’s wealth is their dispute about whether the slave enjoys full ownership or only a deficient ownership. Whoever says that he lacks complete ownership and that his master is the true owner—as every property must have an owner—holds that the zakāh lies with the master. Whoever says that either one of them owns it outright, yet not the master—because possession is in the hand of the slave, yet not firmly so, since the master can confiscate it—holds that no zakāh at all is due on it. Whoever regards mere physical control (yad) over property as sufficient to require zakāh, by analogy with the free man’s control, obligates zakāh on the slave himself—especially those who consider general scriptural commands to encompass both free persons and slaves, and who view zakāh as a form of worship attached to whoever has disposal over wealth.

As for owners whose debts absorb all their assets, or absorb that portion of their wealth on which zakāh would otherwise be due, while they still hold goods subject to zakāh, the jurists also disagreed.
• A group said: No zakāh is payable on any property—grain or otherwise—until the debts have been deducted; if what remains reaches the nisāb, he pays zakāh, and if not, he is exempt. This is the opinion of al-Thawrī, Abū Thawr, Ibn al-Mubārak, and others.
• Abū Ḥanīfah and his companions say: Debt does not prevent the zakāh of grain but does prevent it for all other kinds of wealth.
• Mālik says: Debt prevents the zakāh of ready cash alone, unless the individual owns trade goods sufficient to settle his debt, in which case it does not prevent zakāh.
• Another group, taking the diametrically opposite view of the first, holds that debt never blocks zakāh under any circumstances.