What is the legal ruling on transferring money through an intermediary with whom an exchange rate is agreed upon via WhatsApp, and then the equivalent amount is deposited in another country? Is this transaction considered riba al-nasia (interest due to delay) or a constructive possession (qabd hukmi)? Is communication via WhatsApp considered a "session of possession" (majlis qabd)?

The transaction mentioned is an exchange (sarf), which requires qabḍ (taking possession) at the contract session, either physically or constructively. The separation that precludes the transaction is the separation of the two contracting parties by their bodies from their session. Constructive qabḍ occurs through deposit into an account or a bank transfer at the same time. Contracting through modern communication methods is permissible, but the contract is not concluded except upon acceptance and actual or constructive qabḍ. To regulate this transaction, it is possible to agree on direct transfer of both amounts via mobile phone, or for each party to deposit into the other's bank account and send a picture of the deposit.