Is it permissible to buy and sell foreign currencies, such as the dollar, from a bank via a mobile application, with the intention of profiting from their price increase, if payment and receipt are conducted through deduction and deposit in the same bank account?

It is permissible to buy and sell currencies via mobile phone if constructive possession is achieved, which is the immediate banking entry of the amount. The banking entry is considered a valid constructive possession, whether through direct deposit, bank transfer, a ready exchange contract between the customer and the bank, or by the bank deducting an amount from the customer's account for another account in a different currency. Banks must observe the rules of the exchange contract, and a delay in the banking entry for customary periods is excused, provided that the beneficiary does not dispose of the currency during this period until the effect of the banking entry is realized through the possibility of actual receipt.