The names given to these various forms of sale are derived in two ways: some refer to the nature and circumstances of the contract itself, while others refer to the description of the commodity sold. Whenever the exchange involves one specific asset for another, it must be either money for money, money for goods, or goods for goods. If the exchange is money for money it is called ṣarf (currency exchange). If it is money for goods, it is termed an unrestricted sale—and the same designation applies to goods for goods, provided the conditions that will be mentioned later are observed. When a specific asset is exchanged for a liability the contract is called salām. If the sale is concluded with a contractual option it is called a sale with option (bayʿ al-khiār); if it is based on disclosure of cost price and an agreed profit it is called murābaḥa; and if conducted by competitive bidding it is called muzāyada (auction sale).
Part Two
General Grounds of Invalidity in Unrestricted Sales
Chapter One
Items Whose Sale Is Unlawful
When the legal causes owing to which the Sharīʿah prohibits certain sales—the general grounds of invalidity—are examined, four principal causes emerge:
- The sale of something whose very substance is unlawful.
- Ribā (usury).
- Gharar (excessive uncertainty).
- Stipulations that lead to one or both of the foregoing.
These four, in truth, are the fundamental roots of invalidity, for the prohibition here attaches to the transaction insofar as it is a sale, not because of an external consideration.
As for sales that are forbidden for extraneous reasons, they include: fraud, harm, conflict with a time reserved for something more important, or the fact that the item is itself unlawful to sell.
Accordingly, this Part contains several chapters:
Chapter One: Items Whose Sale Is Unlawful
Such items fall into two categories: impure (najis) substances and substances that are not impure. The primary proof for forbidding the sale of impure substances is the ḥadīth of Jābir, authenticated in both Ṣaḥīḥ collections, in which he said:
“The Messenger of Allah—peace and blessings be upon him—said: ‘Allah and His Messenger have forbidden the sale of wine, carrion, swine, and idols.’”
Someone asked, “O Messenger of Allah, what about the fat of a dead animal? It is used to caulk ships and to light lamps.”
He replied, “May Allah curse the Jews; when its fat was prohibited for them they sold it and consumed its price.”
Concerning wine he also said: “The One who forbade drinking it has likewise forbidden selling it.”
Impure substances themselves are of two kinds: the first enjoys unanimous agreement