Is the aforementioned transfer of money to the professor via a friend with the intention of repaying its equivalent later considered a form of usury (riba)? And what is the exchange rate to be considered at the time of repayment? And how can the money be transferred in a Sharia-compliant way?

To send money to your teacher in another country, there are several legitimate methods: 1. Bank Transfer: Transferring money from a bank in your country to your teacher's account in his country, where the exchange and transfer occur simultaneously. The official exchange receipt is considered a valid receipt. 2. Sending Money via a Traveling Friend: Giving money to a friend who is traveling to deliver it in person to your teacher. This constitutes an agency for delivering the money, and it is permissible to pay a fee to the friend. 3. Authorizing the Friend to Exchange and Deliver: Giving the friend the amount and authorizing him to exchange it into the local currency and deliver it to your teacher.

Important Warning: It is not permissible for your friend to pay your teacher in local currency in exchange for you giving the friend an amount in foreign currency later, as this is considered a deferred exchange and is forbidden. Similarly, it is not permissible to agree in a loan that repayment will be in a currency other than the loan's currency.

If your friend is with you in the same country (Asia) and is not traveling, a valid transaction can be carried out by ensuring immediate possession through a virtual four-party meeting (you and your friend in Asia, and your agent and your friend's agent in your teacher's country). This way, simultaneous possession of both currencies occurs between the agents at the moment you hand over the currency to your friend. Possession by the agent is considered possession by the principal.

The exchange rate is determined by agreement between the two parties and is not required to be equal to the bank's rate.