What is the effect of the agent (Wasil) completing the exchange?
Chapter on Riba (Usury) and Exchange (Sarf)
Al-Mughni
Book of Sales
Primary text
If one party appoints an agent to take possession, and the agent completes the exchange before the principals separate, the Sarf is valid, as the agent's possession stands in place of the principal's possession, irrespective of whether the agent leaves the meeting place before or after taking possession.
Supporting text
If the principals separate before the agent takes possession, the contract is voided because the condition of mutual possession in the sitting has been missed. Furthermore, if the principals exercise their option to cancel (takhayyar) before possession, the contract may be voided according to the Shafi'i school because the contract becomes binding upon agreement, similar to separation. However, the sounder view is that cancellation does not void the contract if possession is subsequently completed within the sitting, as the binding nature of the contract before possession is irrelevant to the validity of the possession condition itself.