Is it permissible to conduct money transfers via an intermediary on WhatsApp, and does this fall under usury of delay (riba al-nasi’ah)? What is the criterion for immediacy, and is WhatsApp suitable as a medium for concluding a contract?

It is permissible to conduct contracts via the Internet and reliable modern communication methods. Audio contracts have the rulings of contracting between those present, and the contracting session is the time of communication. As for written contracts, they have the rulings of contracting between absentees. Seizure ( قبض ) is legally achieved by actual seizure (handover) or constructive seizure (bank entry or vacating with enablement of disposal). When dealing with currencies, mutual seizure must occur before the contracting parties separate. The transaction can be managed by exchanging and depositing the two amounts during a direct audio call via mobile transfer, or by each party depositing into the other's account in the same bank during the call. Delivering the amount to an agent does not achieve mutual seizure unless the agent meets with the other party at the time of transfer.