Q 1: What is the ruling on
taking interest on riyals
which are in the current banknote form. In other words, what is the ruling on depositing such riyals in the bank and receiving a percentage of profit for it, for instance, about 10%.
The ruling on banknotes in this regard is the same as that on gold and silver. It is Haram (prohibited) to deposit banknotes in a bank or the like for a big or small percentage of the deposited sum. Doing so is Riba (usury/interest) which is prohibited by proofs from the Qur'an, Sunnah (whatever is reported from the Prophet), and Ijma` (consensus of scholars).