Is it permissible for him to buy a computer for his son using interest he has received or keep it in return for waiving debts owed to him?

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Check below answers in case you are looking for other related questions:
Can he get rid of interest by giving it to his brother who is in debt?
Ruling on using the returns on investment certificates for postgraduate education

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He has a sister who is not Muslim; she wants to take a riba-based loan then give him a loan without interest
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Can he get rid of interest by giving it to his brother who is in debt?
Ruling on using the returns on investment certificates for postgraduate education

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