Substitution (ibdal) in fiqh

Ibdal, or substitution, means putting one thing in place of another. Lexicographers and jurists use the word and its counterpart istibdal with the same meaning. In fiqh it is a kind of disposition, whose default is permission when made by someone competent over what he may dispose of. The Kuwaiti encyclopedia sets out the schools' differences on where it arises: substituting the obligated item in zakat and expiation, substituting prices and goods before receipt, compulsory substitution in leases, and substituting endowed property. ^{1 2}

Linguistically, ibdal is putting one thing in place of another, and istibdal has the same meaning. The jurists use the two interchangeably, but the encyclopedia notes a narrower usage: ibdal for putting one specific thing in place of another, and istibdal for selling endowed property for cash. ^{1 3}

Most jurists generally forbid substituting the obligated item in zakat and expiation with its value, because the right belongs to God, who fixed it at what is stated. The Hanafis allow substitution by value in these, because for them the obligation attaches to wealth in the sense of its value. ^{1 2}

In exchange contracts such as sale the jurists differ on substituting the prices. The Hanafis allow it before receipt, because prices are not fixed by being specified, and the contract is not annulled if they perish. They cite Ibn Umar's report about exchanging camels for dirhams and dinars, which contains the words "no harm if you separate and nothing remains between you," and they read it as concerning specific money, not debt. The Shafi'is and Zufar among the Hanafis hold that a specified price, whether cash or other, may not be disposed of before receipt, while a price owed as a debt may be substituted. The Hanbalis and Malikis are close to this view. The encyclopedia's footnote notes that al-Shafi'i tied his view to the report's soundness, and that al-Tirmidhi and al-Bayhaqi said only Simak transmitted it in the raised form. ²

The Hanafis do not allow substituting a movable sold item before receipt; the case of real estate is disputed. The Shafi'is do not allow substituting a specified sold item or price before receipt. The Hanbalis allow disposing of the sold item before receipt where it needs no receipt, but not where it does. The Malikis allow disposal before receipt except for food in an exchange. All of this concerns matters other than currency exchange and advance sale, and other than ribawi goods, where substitution is not allowed. ²

Substitution can be obligatory. If a hired animal in a lease on the lessor's liability is found defective, or is shown to belong to another, the lease is not ended; the lessor must replace it. ²

In an endowment, substitution may have its own conditions. It is one of the ten conditions that founders customarily state in their deeds, and founders pair it with istibdal, so that the notaries distinguish the two. ^{2 3}

Rulings on ibdal and istibdal appear across many questions, including zakat, sacrifice, expiation, sale, pre-emption, lease and waqf, and each question is treated in its own place. ³