What is the ruling on the 300 dinars that were received as a percentage of the profits from a loan given to someone, and is it considered usury (riba)? Can it be considered part of the repayment of the interest-free loan (qard hasan) that is due, and is it permissible to demand the remaining amount?

If the amount is a loan, it is not permissible to agree that it should entail a benefit, such as a gift or a percentage of profit, because the purpose of a loan is to show kindness and provide assistance. If the lender stipulates a right for himself, it deviates from its purpose and becomes void. However, if the creditor voluntarily gives something without it being stipulated, it is permissible and even encouraged, based on the hadith: "The best among you are those who are best in paying off debts." Accordingly, it is not permissible to take the 300 dinars as a percentage of profits. They can, however, be considered part of the loan. It is permissible to take the remaining two thousand because they represent the principal amount and are not profit.