Zayf refers to debased or substandard currency compared with the sound coins owed. If a debt requires sound dirhams and inferior dirhams are handed over, the outward count may be correct while the required quality is deficient.
Whether the recipient knew of the defect, accepted the coins, or later discovered it may affect the remedy. Equal numerical amounts do not automatically constitute complete performance when the quality legally due differs.
Application: A debt of 100 sound dirhams cannot be assessed solely by the number 100 if the coins actually tendered are zayf.