Book of Ṣarf (Currency Exchange)
Two conditions are unique to this sale:
- The absence of deferment—that is, settlement must be immediate; and
- The absence of excess—that is, strict equivalence must be maintained.
Because the whole discussion turns on these two requirements, the subject may be reduced to five main categories:
First: discerning what does and does not constitute deferment.
Second: discerning what is and is not deemed equivalent, for each of these two headings branches into numerous sub-sections in which juristic disagreement arises.
Third: examining those forms of currency exchange that have actually occurred yet remain disputed—whether they serve as a means that leads to either of the two prohibitions (increase or deferment), or to both, according to those who apply the principle of blocking the means, chief among them Mālik and his companions. This, too, divides into two kinds, in keeping with its parent division.
Fifth: the distinctive rulings of this sale insofar as the two conditions—no deferment and no disparity, or one of them—must be observed; for in these respects ṣarf differs from other sales in many legal details.
If you consult the works devoted to the sub-topics of what they entitle “The Book of Ṣarf,” you will find that everything returns to these five categories or to composites formed from them—save for questions that authors insert into the very same chapter even though they do not truly belong there. An example is the Mālikīs’ inclusion, under ṣarf, of numerous issues that properly belong to the collection of salam debts. Yet because the defective forms of those dealings ultimately go back to one of the two original prohibitions—namely, currency exchange with deferment or with excess—they placed them here, such as their discussions on demanding what is currently on hand, what is pooled together, or what is owed individually, each from the other.
Our aim, however, is to treat only those matters that are explicitly mentioned in the Revealed Law or stand very close to what is explicit. Accordingly, we shall set out in this book seven well-known questions that function as foundational principles for whatever issues may confront the mujtahid in this field. Indeed, we composed this work so that the student of the discipline might, by means of it, attain the rank of ijtihād—once he has already acquired the requisite amount of knowledge in grammar, language, and the methodology of jurisprudence, an amount no larger (and perhaps smaller) than the size of this very book. At that point he is entitled to be called a jurist (faqīh)—not merely because he has memorized legal questions, even were their number to reach the utmost limits of human retention, as we find many self-styled students of law in our own times imagine.