Did Imam Al-Shafi‘i, in one of his books, permit the sale of the current paper currency, which is neither gold nor silver, considering it as paper that can be bought, sold, traded, and profited from like a commodity? And is this statement correct?

Paper currencies did not exist during the time of Imam Al-Shafi'i. The term "fulus" mentioned in the writings of early scholars referred to metal pieces (iron or copper) smaller than the dinar and dirham. Early scholars differed on whether usury applied to them, and Al-Shafi'i considered them not to be a price for goods, unlike dinars and dirhams. As for paper currencies today, there is no doubt that they serve as a price for goods, just like dinars and dirhams, and therefore take their ruling.